Nonprefixed library functions

This fixes issue #2395.

It is close to working fully in that some tests fail currently.

Notably, everything in ``slow2`` is failing (not sure why) and ``test_dlfcn_stacks`` and ``test_asm_pgo`` are failing in ``slow2asm``.

All of ``default`` is passing however.

This is a requirement for pull request #2240 to be able to land.