[CM] snd/vim integration

[bil at ccrma.Stanford.EDU]

I don't know of any prior work on that.  snd-kbd.c has
the keyboard mappings.  There's an array "built-in-keys"
and a function "keyboard_command".  The latter is
a set of case statements -- it should be reasonably
obvious how it works.  I don't know anything about vim.
If you get something working, please let me know --
I'd be happy to merge it into my version.