New entry points are needed to support built-ins with more parameters.

Also, now that ops that are not function calls don't use the
TIntermAggregate class any more, it's easier to exclude nodes that are
not candidates for built-in emulation using a simple blacklist rather
than to use a whitelist.

Also includes function name style cleanup in BuiltInFunctionEmulator.

This will make it possible to add necessary emulation for built-ins
from ESSL 3.10.

BUG=angleproject:1730
TEST=angle_unittests

Change-Id: If267fc68f5cb9b2ee6703cbcbbe4d157da44a7e0
Reviewed-on: https://chromium-review.googlesource.com/431297
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>