More updates for VC documentation.

More updates for VC documentation.

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

* maintaining.texi (Advanced C-x v v): Use fileset terminology.
(VC With A Merging VCS, VC Change Log): Add xref to VC Pull node.
(VC Pull): Mention vc-log-incoming.
(Log Buffer): Add CVS/RCS only disclaimer.

* vc1-xtra.texi (Remote Repositories): Update introduction.
(Local Version Control): Node deleted (obsolete with DVCSes).
(Remote Repositories, Version Backups): Node deleted.  Move
documentation of vc-cvs-stay-local to CVS Options.
(CVS Options): Reduce verbosity of description of obscure CVS
locking feature.
(Making Revision Tags, Revision Tag Caveats): Merge into Revision
Tags node.
(Revision Tags): Move under Miscellaneous VC subsection.
(Change Logs and VC): Note that this is wrong for DVCSs.
De-document log entry manipulating features.
(Renaming and VC): Describe how it works on modern VCSes.

* programs.texi (Custom C Indent): Add index entries.