libc: Deglob reexports. #11870

Them removes all the glob reexports from liblibc. I did it by removing them all, and then adding back per-platform explicit reexports until everything built again.

I realize this isn't the best strategy for determining an API, but this is the lowest-impact change that solves the problem, plus I'm dissatisfied with the design of this library for other reasons and think it needs to be reconsidered from top to bottom (later).

Progress on #11870.