Builtin precision tests

On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".


Start testcase: precision.sub.lowp_vertex.scalar
FAIL precision.sub.lowp_vertex.scalar: 16028/16784 inputs failed.

Start testcase: precision.sub.lowp_vertex.vec2
FAIL precision.sub.lowp_vertex.vec2: 16684/16784 inputs failed.

Start testcase: precision.sub.lowp_vertex.vec3
FAIL precision.sub.lowp_vertex.vec3: 16706/16784 inputs failed.

Start testcase: precision.sub.lowp_vertex.vec4
FAIL precision.sub.lowp_vertex.vec4: 16710/16784 inputs failed.

Start testcase: precision.sub.lowp_fragment.scalar
FAIL precision.sub.lowp_fragment.scalar: 16028/16784 inputs failed.