Using SDL functions to load libraries, and cross-platform stuff

[Patrice Mandin]

Hello,

As SDL support has been added for audio and video, it would be nice to
also use it to load libraries. This will remove some non-cross platform
stuff.

Also, in code/qcommon/common.c, <winsock.h> is included if system is
neither linux nor macosx, which is wrong. It should be included only on
win32 systems.

There are many more things like that in the source, like
code/game/q_shared.h file that holds many system-dependent stuff, or
code/unix/unix_main.c which is full of #ifdef stuff. This is where
having autotools support would be nice, but I know some people
here don't want it atm.

-- 
Patrice Mandin
WWW: http://pmandin.atari.org/
Programmeur Linux, Atari
Spécialité: Développement, jeux