Someone pointed out that cartographers may think of aspect
at North=0, clockwise, but r.slope.aspect is defined from
a mathmatical point of view (East=0, counterclockwise).

The included are diffs to add a -g flag to produce aspect
maps this way.

main.diffs  (r.slope.aspect/cmd/main.c)
man.diffs (man page)

--Darrell
