* vc1-xtra.texi: Move nodes VC Directory Mode and VC Directory Commands

* vc1-xtra.texi: Move nodes VC Directory Mode and VC Directory Commands
to files.texi.  Move contents of vc2-xtra.texi here.

* vc2-xtra.texi: File removed.

* vc-xtra.texi (Advanced VC Usage): Remove VC Directory Mode and VC
Directory Commands from the submenu.  Don't include deleted file
vc2-xtra.texi.

* files.texi (Visiting): Document find-file-confirm-nonexistent-file.
(Version Control): Add VC Directory Mode and VC Directory Commands to
the submenu.
(Why Version Control?): Use table format.
(Version Control Systems): Note that Meta-CVS support is gone.
(VCS Concepts): Note precisely when VC started supporting filesets.
Remove bogus xref to CVS Options node.
(Types of Log File): Copyedits.
(VC Mode Line): Document tooltips and mouse-1 on VC indicator.
(Basic VC Editing): Content moved from Selecting A Fileset and Doing
The Right Thing.
(Selecting A Fileset, Doing The Right Thing): Nodes deleted.
(Log Buffer): Reorganize node, putting C-c C-c description first.
(Old Revisions): Use CVS for example, not RCS.
(Secondary VC Commands): Remove VC Directory Mode and VC Directory
Commands from the submenu, putting them under Version Control.
(VC Directory Mode): Move node contents here from vc1-xtra.texi; we
need to include it in the manual unconditionally, since it is now
crucial to using distributed version control systems.