Limits of X

[Fred Kiefer]

A drawing problem that Pierre-Yves Rivaill showed me at the FOSDEM
turned out to be caused by the short range of XPoint. This consists of
two shorts allowing numbers from -32768 to 32767. As the functions that
do the conversion to the X coordinates all use gs_floor inline function
we should change this to return short and also to try to correct the
result, e.g. if we end up with a value > SHRT_MAX return SHRT_MAX. 
This is not the best correction we can do, but the only one that can be
done locally. A better change would be to clip any path before drawing
at this boundary (-32768, -32768, 32767, 32767), but for this we would
have to rework a lot of our code.
So if nobody comes up with a brilliant idea, I will just patch
gs_floor()

Fred