This change adds constant folding support for following matrix
built-ins:
    - matrixCompMult, outerProduct, transpose, determinant and
      inverse.

BUG=angleproject:913
TEST=angle_unittests(new: MatrixUtilsTest, ConstantFoldingTest.*Matrix*),
dEQP Tests:
dEQP-GLES3.functional.shaders.constant_expressions.builtin_functions.matrix.*
(All 54 tests started passing with this change)

Change-Id: I7b9bf04b9a2cbff72c48216cab04df58c5f008d6
Reviewed-on: https://chromium-review.googlesource.com/276574Reviewed-by: Olli Etuaho <oetuaho@nvidia.com>
Tested-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>