The hash values used for looking up built-ins now encode the string
length and the location of parentheses as six-bit values, so that we
don't need to check for these if the hash matches.

This decreases shader_translator binary size on Windows by around 10
KB.

BUG=angleproject:2267
BUG=chromium:823856
TEST=angle_unittests

Change-Id: If8c28e1c8851750633509ec6273f556e06e91cd1
Reviewed-on: https://chromium-review.googlesource.com/973243Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>