MSAA and A2C support

See bird/Kart-Public@6de93448

Adds MSAA anti-aliasing and Alpha to Coverage(A2C), available with -msaa and -a2c (requires -msaa )

MSAA requires a sample size after the -msaa parameter. The available sample sizes are 2, 4, 8 and 16. Higher sample sizes will run worse but look better

Comparison

MSAA(4x)	No MSAA

A2C	No A2C