This change adds ANGLE support for isnan/isinf.

BUG=angle:922
TEST=dEQP tests:
dEQP-GLES3.functional.shaders.builtin_functions.common.isnan.*
(high precision tests still fail)
Tests passing 100% because of this change:
dEQP-GLES3.functional.shaders.builtin_functions.common.isinf.*
Reduced number of errors in tests:
EQP-GLES3.functional.shaders.constant_expressions.builtin_functions.common.isnan.*
dEQP-GLES3.functional.shaders.constant_expressions.builtin_functions.common.isinf_*

Change-Id: I52bf18b59365ea7031746ae840550162d7e6b96e
Reviewed-on: https://chromium-review.googlesource.com/250761Reviewed-by: Olli Etuaho <oetuaho@nvidia.com>
Tested-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Nicolas Capens <capn@chromium.org>