Allow count before OMAPed motion.

Count before OMAP refused to work unless the mapping is also present in
the normal mode map (defeating the purpose of OMAP).

Example:
:onoremap L $<Ret>
d4L

This should delete 4 lines and it is now supported.
Don't let dfX be influenced by OMAP

f/F/t/T motions should never pick up on single-character OMAP mappings,
make sure to switch to NO_KEYMAP instead.

A better fix would be to disallow suffix matches, rendering NO_KEYMAP
obsolete.