Merge from origin/emacs-25

eaa00584ce Improve documentation of 'gnutls-verify-error'
908498cc01 ; etc/PROBLEMS: Describe GTK-related crashes on elementar...
741daec617 ; Describe the problem with ksh when resizing shell window

etc/PROBLEMS

@@ -217,6 +217,28 @@ result in an endless loop.
 If you need Emacs to be able to recover from closing displays, compile
 it with the Lucid toolkit instead of GTK.
 
+** Emacs compiled with GTK crashes at startup due to X protocol error.
+
+This is known to happen on elementary OS GNU/Linux systems.
+
+The error message is:
+
+  X protocol error: BadMatch (invalid parameter attributes) on protocol request 140
+  When compiled with GTK, Emacs cannot recover from X disconnects.
+  This is a GTK bug: https://bugzilla.gnome.org/show_bug.cgi?id=85715
+  For details, see etc/PROBLEMS.
+  Fatal error 6: Aborted
+
+followed by a C backtrace.  (Sometimes the offending protocol request
+number is 139.)
+
+The relevant bug report is here:
+
+  https://bugs.launchpad.net/elementaryos/+bug/1355274
+
+A workaround is to set XLIB_SKIP_ARGB_VISUALS=1 in the environment
+before starting Emacs, or run Emacs as root.
+
 ** Emacs crashes when you try to view a file with complex characters.
 
 For example, the etc/HELLO file (as shown by C-h h).
@@ -469,6 +491,17 @@ problem by adding this to your .cshrc file:
         stty -icrnl -onlcr -echo susp ^Z
     endif
 
+*** In Shell buffers using ksh, resizing a window inserts random characters.
+
+The characters come from the PS2 prompt, but they are not followed by
+a newline, which messes up the next command you type.  This strange
+effect is caused by Emacs 25 and later telling the shell that its
+screen size changed.
+
+To work around the problem, customize the option
+'window-adjust-process-window-size-function' to "Do not adjust process
+window sizes" (Lisp value 'ignore').
+
 *** In Inferior Python mode, input is echoed and native completion doesn't work.
 <https://debbugs.gnu.org/cgi/bugreport.cgi?bug=25753>
 

lisp/net/gnutls.el

@@ -52,7 +52,27 @@ set this variable to \"normal:-dhe-rsa\"."
                  string))
 
 (defcustom gnutls-verify-error nil
-  "If non-nil, this should be a list of checks per hostname regex or t."
+  "If non-nil, this should be t or a list of checks per hostname regex.
+If nil, the default, failures in certificate verification will be
+logged (subject to `gnutls-log-level'), but the connection will be
+allowed to proceed.
+If the value is a list, it should have the form
+
+   ((HOST-REGEX FLAGS...) (HOST-REGEX FLAGS...) ...)
+
+where each HOST-REGEX is a regular expression to be matched
+against the hostname, and FLAGS is either t or a list of
+one or more verification flags.  The supported flags and the
+corresponding conditions to be tested are:
+
+  :trustfiles -- certificate must be issued by a trusted authority.
+  :hostname   -- hostname must match presented certificate's host name.
+  t           -- all of the above conditions are tested.
+
+If the condition test fails, an error will be signaled.
+
+If the value of this variable is t, every connection will be subjected
+to all of the tests described above."
   :group 'gnutls
   :version "24.4"
   :type '(choice