Reduced skslc memory consumption

The big change here is smarter generic type handling which allows us to
keep far fewer entries in the core symboltable. This also comments out
a number of OpenGL builtin functions which Skia does not use and is
unlikely to in the future.
BUG=655673
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2442063002

Review-Url: https://codereview.chromium.org/2442063002
9 files changed