This prefixes a key with all of the different meta prefixes and returns a list of the prefixed strings.
takes a keymap, a base key specification, and a function name; it prefixes the base key with all ``meta'' combination prefixes, and installs the new combinations into the keymap. For example, (keymap:send-map-function-meta keymap "a" func) maps all of ``m:a'' and ``ESC;a'' to func.