Only compile test with GL & SDL, don't compile test with optimizations
Implement _EXPECT_VEC3_EQ and _EXPECT_VEC4_EQ

Useful for testing equivalence of vec3s and vec4s.
Implement negation of vectors
Implement floor, fract, sign and mix
Make float_eq able to handle negative values, and increase epsilon
Make shader test report expected and actual values
Implement atan with two arguments