Just the minimial changes to get this to actually build, because otherwise
we always bog down trying to rewrite everything (when the real answer
is usually "stop using libcutils, it's awful").
This doesn't move a handful of files: two are basically just BSD libc
source, a couple have outstanding code reviews, and one can be deleted
(but I'll do that in a separate change).
I'm also skipping the presubmit hooks because otherwise clang-format
wants to reformat everything. I'll follow up with that...
Bug: N/A
Test: builds
Change-Id: I06403f465b67c8e493bad466dd76b1151eed5993
Also simplifies the Darwin implementation of gettid, because
apparently libbacktrace had a better way of doing it.
Change-Id: I9e14f9176b167405a5aaa5b8a0db0327c7126271
