[Kst] round -> rint ?

[Brisset, Nicolas]

I have had to change round(...) calls to rint(...) calls in
kstgfxmousehandlerutils.cpp to get it to compile on my Solaris 8 box. If
nobody minds I'd like to commit that to trunk & 1.3 since it seems to be
more portable. I am not sure whether there are cases where the results
differ, and I have no idea of the impact a difference (at most 1) could
have.

Nicolas