-Fixes for OpenGL 3.0 after merge
-No longer specify GLFW_OPENGL_VERSION_MINOR so that 3.0 users can use 3.0, and 3.2+ users can use 3.2+.
-Restored texture2D() funcs back to texture() (texture2D is deprecated)
-Revised configure.ac to check for either Apple or Linux/mingw OpenGL header file locations
-mingw bullet location should be /usr/include/bullet in configure.ac
-Lowered antialiasing to 2x for performance reasons
-Added (commented out) library version checks via pkg-config