Make SDL2 work better
Make SDL2 work better

* Fix a compilation problem on gcc2
* Use dlopen for shared library suport, as the custom code doesn't look
for libs in the right place (fixes libSDL2 not finding libpng, for
example).

Begasus/haikuports,nielx/haikuports,haikuports/haikuports,haikuports/haikuports,moochris/haikuports,koletzky/haikuports,nielx/haikuports,miqlas/haikuports,koletzky/haikuports,Begasus/haikuports,moochris/haikuports,haikuports/haikuports,haikuports/haikuports,nielx/haikuports,Begasus/haikuports,Begasus/haikuports,haikuports/haikuports,miqlas/haikuports,koletzky/haikuports,moochris/haikuports,miqlas/haikuports,Begasus/haikuports