Start adjusting the manuals to talk about the keymap-* functions

Start adjusting the manuals to talk about the keymap-* functions

* lisp/dired.el (dired--make-directory-clickable):
* doc/lispref/keymaps.texi (Keymaps):
(Key Sequences):
(Prefix Keys):
(Active Keymaps):
(Key Lookup):
(Functions for Key Lookup):
(Changing Key Bindings):
(Key Binding Commands):
(Tool Bar):
* doc/lispref/commands.texi (Interactive Codes):
(Event Examples):
(Event Mod):
* doc/emacs/kmacro.texi (Save Keyboard Macro):
* doc/emacs/custom.texi (Keymaps):
(Keymaps):
(Minibuffer Maps):
(Rebinding):
(Init Rebinding):
(Modifier Keys):
(Mouse Buttons):
(Init Examples):
(Init Non-ASCII): Adjust the documentation to remove description
of the old syntaxes, and use the new keymap-* functions.

* doc/lispref/keymaps.texi (Low-Level Key Binding): New node that
describes `define-key' and the old key syntaxes.