fix casts on variable writes
pick smallest vector type when many would satisfy type inference
fix size of inferred vectors for swizzles like .ra
print 1+ and 1- correctly
update built-in variables/constants
update todo list
require RETURN, handle inference on return values better
rewrite finalize-inference, fix bugs
add printers for incf,decf,++,--
update shader todo list
remove type declarations from skybox shader to test type inference
use glsl 440 header for now