Another James Harvey patch. This one introduces a new button code
called `CURSOR_SELECT', intended for platforms which have a fire
button to go with their cursor keys. (Apparently some Palms do.)
CURSOR_SELECT is not bound to anything on any of the current three
platforms, and therefore no game may rely on it being available.
This checkin adds it in Net as a synonym for 'a', the keyboard-based
rotate-left command.

[originally from svn r5915]