Statically allocate built-in function symbols A script gen_builtin_symbols.py now generates code for initializing built-in function symbols. The TFunction objects are initialized at C++ compile time. The source file used for the functions is in a format that's similar to how functions are given out in the GLSL spec, so it is easy to maintain. The function symbols are still inserted to the symbol table levels same as before. Getting rid of inserting the symbols at runtime is intended to be done as follow-up. This speeds up angle_unittests on Linux in release mode by a bit less than half, and in debug mode by more than half. BUG=angleproject:2267 TEST=angle_unittests Change-Id: I11c9de98c74d28e7e8cdf024516e2f6ee30ca33e Reviewed-on: https://chromium-review.googlesource.com/924155 Commit-Queue: Olli Etuaho <oetuaho@nvidia.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>