swift234

Add a stand-alone generic specializer pass.

Begin unbundling devirtualization, specialization, and inlining by
recreating the stand-alone generic specializer pass.

I've added a use of the pass to the pipeline, but this is almost
certainly not going to be the final location of where it runs. It's
primarily there to ensure this code gets exercised.

Since this is running prior to inlining, it changes the order that some
functions are specialized in, which means differences in the order of
output of one of the tests (one which similarly changed when
devirtualization, specialization, and inlining were bundled together).