The Makefile and main.c arranged to put "netbsd-${DATE}" into the
executable. Remove this so that different compiles can be binary
compared. rcsid's for all files are already embedded in the executable
so versions can be easily distinguished. (I didn't catch this on
previous passes because I did my builds on the same day.)

Note: there's a special rule for main.o in Makefile with a purpose I
can't actually discern -- I think it isn't needed, and I've flagged it
with a comment.

(perry)