From: Jonathan Atkins
Subject: [SDL] SDL_SaveBMP width bugfix

this fixes the pitch versus width difference that can happen
(especially for 8bit and 24bit (with the exact RGBAmasks) surfaces)
when you use SDL_SaveBMP.  The problem was the pitch was used
instead of the width, which in some cases is much wider than the
screen area you really want to save...making for ugly crud on the
saved image borders.
This code has been tested with & without pitch overhangs...and
with the right masks for 24 bit surfaces.
I tested 8,15,16,24,32-0RGB,32-RGBA(with no SDL_SRCALPHA flag).

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%401013