Update Android port

* configure.ac (ANDROID_STUBIFY): Add androidvfs.o when building
libemacs.so.
* doc/emacs/android.texi (Android): Add `Android Document Providers'.
(Android Startup): Update the location of the content identifier
directory.
(Android File System): Describe access to document provider
directories.
(Android Document Providers): New node.
* doc/emacs/emacs.texi (Top): Update the menu for the Android
appendix.
* java/Makefile.in (filename, install_temp/assets/build_info): Make
directory-tree depend on build_info.
* java/org/gnu/emacs/EmacsActivity.java (onActivityResult): New
function.  When a document tree is accepted, persist access to it.
* java/org/gnu/emacs/EmacsDirectoryEntry.java (EmacsDirectoryEntry):
New struct.
* java/org/gnu/emacs/EmacsOpenActivity.java (checkReadableOrCopy): Use
EmacsService.buildContentName.
* java/org/gnu/emacs/EmacsService.java (getEmacsView, openContentUri)
(checkContentUri): Remove excessive debug logging.
(buildContentName, getDocumentAuthorities, requestDirectoryAccess)
(getDocumentTrees, decodeFileName, documentIdFromName, getTreeUri)
(statDocument, accessDocument, openDocumentDirectory, readDirectoryEntry)
(openDocument, createDocument): New functions.

* lib-src/asset-directory-tool.c: Improve commentary by illustrating
the difference between directory and ordinary files.

* src/android.c (ANDROID_THROW, enum android_fd_table_entry_flags)
(struct android_emacs_service, android_extract_long)
(android_scan_directory_tree, android_is_directory)
(android_get_asset_name, android_url_encode, android_content_name_p)
(android_get_content_name, android_check_content_access, android_fstat)
(android_fstatat, android_file_access_p, android_hack_asset_fd_fallback)
(android_detect_ashmem, android_hack_asset_fd, android_close_on_exec)
(android_open, android_close, android_fclose, android_create_lib_link)
(android_faccessat, struct android_dir, android_opendir, android_dirfd)
(android_readdir, android_closedir, android_lookup_asset_directory_fd)
(android_exception_check_3, android_get_current_api_level)
(android_open_asset, android_close_asset, android_asset_read_quit)
(android_asset_read, android_asset_lseek, android_asset_fstat): Move
content and asset related functions to androidvfs.c.
(android_init_emacs_service): Obtain handles for new JNI functions.
(initEmacsParams): Initialize the VFS layer.
(android_request_directory_access): New function.
(android_display_toast): Remove unused function.

* src/android.h (android_get_current_api_level): Assume that
this function never returns less than __ANDROID_API__.
(struct android_emacs_service): Move `struct
android_emacs_service' here.

* src/androidfns.c (Fandroid_request_directory_access): New
interactive function.
(syms_of_androidfns): Register new subr.

* src/androidvfs.c (struct android_vdir, struct android_vops)
(struct android_vnode, struct android_special_vnode)
(enum android_vnode_type, struct android_cursor_class)
(struct emacs_directory_entry_class)
(struct android_parcel_file_descriptor_class)
(android_init_cursor_class, android_init_entry_class)
(android_init_fd_class, android_vfs_canonicalize_name)
(struct android_unix_vnode, struct android_unix_vdir, unix_vfs_ops)
(android_unix_name, android_unix_vnode, android_unix_open)
(android_unix_close, android_unix_unlink, android_unix_symlink)
(android_unix_rmdir, android_unix_rename, android_unix_stat)
(android_unix_access, android_unix_mkdir, android_unix_readdir)
(android_unix_closedir, android_unix_dirfd, android_unix_opendir)
(android_extract_long, android_scan_directory_tree)
(android_is_directory, android_init_assets)
(android_hack_asset_fd_fallback, android_detect_ashmem)
(android_hack_asset_fd, struct android_afs_vnode)
(struct android_afs_vdir, struct android_afs_open_fd, afs_vfs_ops)
(android_afs_name, android_afs_initial, android_close_on_exec)
(android_afs_open, android_afs_close, android_afs_unlink)
(android_afs_symlink, android_afs_rmdir, android_afs_rename)
(android_afs_stat, android_afs_access, android_afs_mkdir)
(android_afs_readdir, android_afs_closedir, android_afs_dirfd)
(android_afs_opendir, android_afs_get_directory_name)
(struct android_content_vdir, content_vfs_ops)
(content_directory_contents, android_content_name)
(android_content_open, android_content_close)
(android_content_unlink, android_content_symlink)
(android_content_rmdir, android_content_rename)
(android_content_stat, android_content_access)
(android_content_mkdir, android_content_readdir)
(android_content_closedir, android_content_dirfd)
(android_content_opendir, android_content_get_directory_name)
(android_content_initial, android_get_content_name)
(android_check_content_access, struct android_authority_vnode)
(authority_vfs_ops, android_authority_name, android_authority_open)
(android_authority_close, android_authority_unlink)
(android_authority_symlink, android_authority_rmdir)
(android_authority_rename, android_authority_stat)
(android_authority_access, android_authority_mkdir)
(android_authority_opendir, android_authority_initial)
(struct android_saf_root_vnode, struct android_saf_root_vdir)
(saf_root_vfs_ops, android_saf_root_name, android_saf_root_open)
(android_saf_root_close, android_saf_root_unlink)
(android_saf_root_symlink, android_saf_root_rmdir)
(android_saf_root_rename, android_saf_root_stat)
(android_saf_root_access, android_saf_root_mkdir)
(android_saf_root_readdir, android_saf_root_closedir)
(android_saf_root_dirfd, android_saf_root_opendir)
(android_saf_root_initial, android_saf_root_get_directory)
(android_saf_stat, android_saf_access)
(struct android_saf_tree_vnode, struct android_saf_tree_vdir)
(saf_tree_vfs_ops, android_document_id_from_name)
(android_saf_tree_name, android_saf_tree_open)
(android_saf_tree_close, android_saf_tree_unlink)
(android_saf_tree_symlink, android_saf_tree_rmdir)
(android_saf_tree_rename, android_saf_tree_stat)
(android_saf_tree_access, android_saf_tree_mkdir)
(android_saf_tree_opendir_1, android_saf_tree_readdir)
(android_saf_tree_closedir, android_saf_tree_dirfd)
(android_saf_tree_opendir, android_saf_tree_from_name)
(android_saf_tree_get_directory, android_saf_file_vnode)
(saf_file_vfs_ops, android_saf_file_name, android_saf_file_open)
(android_saf_file_unlink, android_saf_file_rmdir)
(android_saf_file_opendir, android_close_parcel_fd)
(android_saf_new_vnode, android_saf_new_name, android_saf_new_open)
(android_saf_new_unlink, android_saf_new_symlink)
(android_saf_new_rmdir, android_saf_new_rename)
(android_saf_new_stat, android_saf_new_access)
(android_saf_new_mkdir, android_saf_new_opendir, root_vfs_ops)
(special_vnodes, android_root_name, android_name_file)
(android_vfs_init, android_open, android_unlink, android_symlink)
(android_rmdir, android_mkdir, android_renameat_noreplace)
(android_rename, android_fstat, android_fstatat_1, android_fstatat)
(android_faccessat, android_fdopen, android_close, android_fclose)
(android_open_asset, android_close_asset, android_asset_read_quit)
(android_asset_read, android_asset_lseek, android_asset_fstat)
(android_opendir, android_dirfd, android_readdir)
(android_closedir): Move file system emulation routines here.
Introduce a new ``VFS'' layer for translating between
Emacs-specific file names and the various disparate interfaces
for accessing files on Android.

* src/callproc.c (delete_temp_file):
* src/charset.c (load_charset_map_from_file):
* src/dired.c:
* src/emacs.c (Fkill_emacs):
* src/fileio.c (check_mutable_filename, Fcopy_file)
(Fmake_directory_internal, Fdelete_directory_internal)
(Fdelete_file, Frename_file, Fadd_name_to_file)
(Fmake_symbolic_link, file_accessible_directory_p, Fset_file_modes)
(Fset_file_times, write_region):
* src/filelock.c (get_boot_time, rename_lock_file)
(create_lock_file, current_lock_owner, unlock_file):
* src/image.c (slurp_file, png_load_body, jpeg_load_body):
* src/keyboard.c (Fopen_dribble_file):
* src/lisp.h:
* src/lread.c (Fload):
* src/process.c (handle_child_signal):
* src/sysdep.c (init_standard_fds, emacs_fopen, emacs_fdopen)
(emacs_unlink, emacs_symlink, emacs_rmdir, emacs_mkdir)
(emacs_renameat_noreplace, emacs_rename):
* src/term.c (Fresume_tty, init_tty): Use and add new wrappers
for fopen, fdopen, unlink, symlink, rmdir, mkdir,
renameat_norepalce and rename.

lib-src/asset-directory-tool.c

@@ -45,7 +45,12 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
    the first file or directory, a NULL byte and an unsigned int
    indicating the offset from the start of the file to the start of
    the next sibling.  Following that is a list of subdirectories or
-   files in the same format.  The long is stored LSB first.  */
+   files in the same format.  The long is stored LSB first.
+
+   Directories can be distinguished from ordinary files through the
+   last bytes of their file names (immediately previous to their
+   terminating NULL bytes), which are set to the directory separator
+   character `/'.  */