Returns the upper-left 2x2 section of a 3x3 matrix.
Original signature is 'GLKMatrix2 GLKMatrix3GetMatrix2 ( GLKMatrix3 matrix );'
Available in OS X x0.8 and later.
public static GLKMatrix2 GetMatrix2 (GLKMatrix3 matrix) { GLKMatrix2 m = new GLKMatrix2 (matrix [0], matrix [1], matrix [3], matrix [4]); return m; }