Add binding in KEYMAP for KEY => DEFINITION, right after AFTER's binding.
This is like `define-key' except that the binding for KEY is placed
just after the binding for the event AFTER, instead of at the beginning
of the map. Note that AFTER must be an event type (like KEY), NOT a command
If AFTER is t or omitted, the new binding goes at the end of the keymap.
AFTER should be a single event type--a symbol or a character, not a sequence.
Bindings are always added before any inherited map.
The order of bindings in a keymap only matters when it is used as
a menu, so this function is not useful for non-menu keymaps.