* frames.texi (Frames): Clean up introduction. Document `ns'

* frames.texi (Frames): Clean up introduction.  Document `ns'
return value for framep.
(Creating Frames): Note how the terminal is chosen.
(Multiple Terminals, Multiple Displays): Merge into a single node.
(Color Parameters): Fix typo.

* variables.texi (Local Variables, Buffer-Local Variables)
(Creating Buffer-Local): Change link to Multiple Terminals.

* os.texi (X11 Keysyms): Change link to Multiple Terminals.

* keymaps.texi (Controlling Active Maps): Change link to Multiple
Terminals.

* commands.texi (Command Loop Info, Keyboard Macros): Change link
to Multiple Terminals.

* elisp.texi (Top): Update node listing.
* vol2.texi (Top): Update node listing.
* vol1.texi (Top): Update node listing.