Move VC diff ASYNC argument to the fifth position

* lisp/vc/vc-svn.el (vc-svn-diff):
* lisp/vc/vc-src.el (vc-src-diff):
* lisp/vc/vc-sccs.el (vc-sccs-diff):
* lisp/vc/vc-rcs.el (vc-rcs-diff):
* lisp/vc/vc-mtn.el (vc-mtn-diff):
* lisp/vc/vc-hg.el (vc-hg-diff):
* lisp/vc/vc-git.el (vc-git-diff):
* lisp/vc/vc-dav.el (vc-dav-diff):
* lisp/vc/vc-cvs.el (vc-cvs-diff):
* lisp/vc/vc-bzr.el (vc-bzr-diff):
* lisp/obsolete/vc-arch.el (vc-arch-diff): Move ASYNC argument to the end.

* lisp/vc/vc.el (vc-diff-internal): Pass `async' argument to the
backend `diff' command in the last position.
* lisp/fringe.el (fringe-bitmap-p): Fix 2014-12-05 breakage.
Fix Semantic completion-at-point functions in non-Semantic buffers

Fixes: debbugs:19077

* lisp/cedet/semantic.el (semantic-analyze-completion-at-point-function)
(semantic-analyze-notc-completion-at-point-function)
(semantic-analyze-nolongprefix-completion-at-point-function): Do
nothing if the current buffer is not using Semantic.
Provide custom-prompt-customize-unsaved-options.

* doc/emacs/custom.texi (Saving Customizations): Mention
`custom-prompt-customize-unsaved-options'.

* etc/NEWS: Mention `custom-prompt-customize-unsaved-options'.

* etc/TODO: Remove its entry.

* lisp/cus-edit.el (custom-prompt-customize-unsaved-options): Add a
mechanism for prompting user about unsaved customizations.
(Bug#19328)