More updates to Maintaining chapter of Emacs manual.

More updates to Maintaining chapter of Emacs manual.

* files.texi (Misc File Ops): Mention vc-delete-file.

* maintaining.texi (Tags): Mention Semantic.
(Create Tags Table, Etags Regexps): Copyedits.
(Find Tag): Mention minibuffer completion.
(List Tags): Mention completion-at-point.  Completion is actually
available in M-x list-tags.

* programs.texi (Symbol Completion): Mention completion-at-point
explicitly.

* vc1-xtra.texi (VC Delete/Rename): Rename from Renaming and VC.
Document vc-delete-file.