quatAndPosToMatrix

auto q = rquat.fromAngle( PI_2, vec3(0,0,1) );
auto m = quatAndPosToMatrix(q, vec3(1,2,3) );
assert( eq_approx( m, [[0,-1,0,1],
                       [1, 0,0,2],
                       [0, 0,1,3],
                       [0, 0,0,1]], 1e-7 ) );