Fix glGet wrappers.

Forgot the v suffix on them, so that's tedious, but what can you do.
Prefix all glGetString property wrappers with gl_.

This ensures that if made included somewhere, it probably won't replace
anything important -- this is especially applicable to methods like
version and vendor, which could potentially be very important symbols
for another included module.
Version 1.2.0

AKA version pretend-version-1.1.0-never-happened.