Doc updates for several Emacs 24.4 changes.

Doc updates for several Emacs 24.4 changes.

* doc/lispref/commands.texi (Event Input Misc): Document new arg to
input-pending-p.

* doc/lispref/display.texi (Font Selection): Tweak example.

* doc/lispref/keymaps.texi (Active Keymaps): Re-organize the text.
(Searching Keymaps): Rewrite the pseudo-code for 24.4 changes.
(Controlling Active Maps): Note that set-transient-map uses
overriding-terminal-local-map.

* doc/lispref/nonascii.texi (Specifying Coding Systems): Don't refer to
emacs-mule-dos.
(Lisp and Coding Systems): Describe emacs-mule return value in
modern terms.

* doc/lispref/tips.texi (Coding Conventions): Tweak the coding system tip;
Emacs now uses utf-8 by default for Emacs Lisp source files.

* doc/emacs/glossary.texi (Glossary): Define MULE in modern terms.

* src/keyboard.c (Voverriding_terminal_local_map):
(Voverriding_local_map): Doc fix.

* src/keymap.c (Vemulation_mode_map_alists): Doc fix.