Continue without sound if OpenAL setup fails

This is potential fix for #221 - I can't reproduce the problem though

I was surprised that sound works even without loading the OpenAL libraries. As is turned out, `AL.create()` does the same thing (and a few things more):

http://grepcode.com/file/repo1.maven.org/maven2/org.lwjgl.lwjgl/lwjgl/2.9.0/org/lwjgl/openal/AL.java?av=f#109

If you guys agree, I remove the OpenAL library loading from `LWJGLHelper`

*Sidenote:* LwjglAudio did not inherit the `synchronized` attribute before. Maybe remove the method stub?