* lisp/emacs-lisp/eldoc.el (eldoc-documentation-function): Describe how
major modes should use `add-function' to alter value of the variable.
* lisp/hexl.el (hexl-mode): Set `eldoc-documentation-function' using
`add-function' so the default value is always used.
* lisp/ielm.el (inferior-emacs-lisp-mode): Set
`eldoc-documentation-function' using `add-function' so the default
value is always used.
* lisp/progmodes/cfengine.el (cfengine3-mode): Set
`eldoc-documentation-function' using `add-function' so the default
value is always used.
* lisp/progmodes/elisp-mode (emacs-lisp-mode): Set
`eldoc-documentation-function' using `add-function' so the default
value is always used.
* lisp/progmodes/octave.el (octave-mode): Set
`eldoc-documentation-function' using `add-function' so the default
value is always used.
* lisp/progmodes/python.el (python-mode): Set
`eldoc-documentation-function' using `add-function' so the default
value is always used.
* lisp/simple.el (read--expression): Set `eldoc-documentation-function'
using `add-function' so the default value is always used.
* lisp/emacs-lisp/find-func.el (find-function-library): Return a pair
(ORIG-FUNCTION . LIBRARY) instead of just its second element.
(find-function-noselect): Use it.
* lisp/progmodes/elisp-mode.el (elisp--xref-identifier-file): Rename to
`elisp--xref-identifier-location', incorporate logic from
`elisp--xref-find-definitions', use the changed
`find-function-library' return value.
* lisp/emacs-lisp/find-func.el (find-function-library): New function,
extracted from `find-function-noselect'.
* lisp/progmodes/elisp-mode.el (elisp--identifier-location): Fold back
into `elisp--company-location'.
(elisp--identifier-completion-table): Rename to
`elisp--identifier-completion-table', and do not include just any
symbols with a property list.
(elisp-completion-at-point): Revert the 2014-12-25 change.
(elisp--xref-identifier-file): New function.
(elisp--xref-find-definitions): Use it.
* lisp/progmodes/xref.el (xref-elisp-location): New class.
(xref-make-elisp-location): New function.
(xref-location-marker): New implementation.
* lisp/progmodes/elisp-mode.el (elisp--xref-find-definitions):
Filter out nil results.
(elisp--xref-find-apropos): New function.
(elisp-xref-find): Use it.
* lisp/progmodes/xref.el (xref--show-xrefs): Use `user-error'.
Move autoloaded bindings for `M-.', `M-,', `C-x 4 .' and
`C-x 5 .' from etags.el to xref.el.
* progmodes/xref.el: New file.
* progmodes/elisp-mode.el (elisp--identifier-types): New variable.
(elisp--identifier-location): New function, extracted from
`elisp--company-location'.
(elisp--company-location): Use it.
(elisp--identifier-completion-table): New variable.
(elisp-completion-at-point): Use it.
(emacs-lisp-mode): Set the local values of `xref-find-function'
and `xref-identifier-completion-table-function'.
(elisp-xref-find, elisp--xref-find-definitions)
(elisp--xref-identifier-completion-table): New functions.
* progmodes/etags.el (find-tag-marker-ring): Mark obsolete in
favor of `xref--marker-ring'.
(tags-lazy-completion-table): Autoload.
(tags-reset-tags-tables): Use `xref-clear-marker-stack'.
(find-tag-noselect): Use `xref-push-marker-stack'.
(pop-tag-mark): Make an alias for `xref-pop-marker-stack'.
(etags--xref-limit): New constant.
(etags-xref-find, etags--xref-find-definitions): New functions.
* lisp/minibuffer.el (completion-table-dynamic): Add arg `switch-buffer'
and change default to stay in the minibuffer when called from
the minibuffer.
(lazy-completion-table): Use this new argument to preserve the
old behavior.
* lisp/progmodes/elisp-mode.el (elisp--local-variables): Don't burp on
incorrect lexical elements (bug#19250).
