[AD] Asm optimized version of _linear_draw_trans_rgba_rle_sprite24 is buggy?

[Serge Semashko <serge@xxxxxxxxxx>]

Hello all,

I started making a fast sprites blitting mini-library with alpha
transparency support for use in ufo2000 (to support alpha transparency
and different brightness level for sprites in an efficient way):
http://lxnt.info:8888/repos/ufo2k/trunk/src/sprite.h
http://lxnt.info:8888/repos/ufo2k/trunk/src/sprite.cpp

While testing 24-bit color support with allegro 4.2.0rc2 on windows, the
program crashes. Rebuilding allegro with ALLEGRO_USE_C resolves the
problem.

I'm going to make some kind of regression testing and benchmarking
framework a bit later, so a real test program reproducing the problem
will be available too.