0m0.198s: Dispatch directly to functions.

Replace (mostly) the *instruments*-based array lookup and invocation
with calling the functions directly. This avoids a painful XEP entry
point check.

real  0m0.198s
user  0m0.194s
sys 0m0.003s
0m0.186s: Allow some inlining.

real  0m0.186s
user  0m0.182s
sys 0m0.003s
0m0.153s: Assume that args to add/gt are integers.

This avoids some generic dispatch.

real  0m0.153s
user  0m0.149s
sys 0m0.003s
0m0.073s: Assume arg1 / arg2 are always integers.

I don't like this as it breaks generality.

real  0m0.073s
user  0m0.069s
sys 0m0.003s