Reduced skslc memory consumption

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

Committed: https://skia.googlesource.com/skia/+/cffaa70896fa5bc6c7bf98abbaafb1a755b49762
Review-Url: https://codereview.chromium.org/2442063002