Directly call glue functions when we can instead of picking them out of the type descriptor

[pcwalton]

We always pull type glue out of a type descriptor to call it, even when the type descriptor in question is statically known. This makes debugging the generated code harder and makes LLVM do more work than it needs to to clean it up.

[graydon]

Is this done? I do not know if we even have glue functions anymore.

[pcwalton]

Made irrelevant by monomorphization.