Merge pull request #217 from erwincoumans/master

fix more warnings, implement missing X11 function for dynamic loading
Merge pull request #218 from erwincoumans/master

remove a lot of warnings (more todo in demos and serialization code)
Update ImportURDFSetup.cpp

fix signed/unsigned warning
Merge pull request #219 from erwincoumans/master

fix another warning
cmake+premake disable OpenGL 3 demos on Mac OSX versions below 10.9
See also http://www.bulletphysics.org/Bullet/phpBB3/viewtopic.php?f=9&t=10073
Move ConstraintPhysicsSetup to Demos3/bullet3/ConstraintDemo