Add ESSL 3.10 ldexp/frexp builtins This adds new built-ins found in ESSL 3.10 section 8.3 Common Functions. This includes constant folding support for ldexp and support for both GLSL and HLSL output. In HLSL these functions need to be emulated. BUG=angleproject:1730 TEST=angle_unittests Change-Id: I1330e69978b0cf53efbc3416150194764414e96c Reviewed-on: https://chromium-review.googlesource.com/435342 Reviewed-by: Corentin Wallez <cwallez@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>