Also fix the signature of usleep, and the definition of useconds_t which
should be unsigned, as the 'u' in its name implies.
This patch also cleans up the existing FreeBSD hacks by moving the libm
stuff from <sys/cdefs.h> to a libm-private header, and adding comments
about the hacks we use to build FreeBSD source.
Change-Id: Ibe5067a380502df94a0a3a7901969b35411085b6
This is actually a slightly newer upstream version than the one I
originally pulled. Hopefully now it's in upstream-freebsd it will
be easier to track upstream, though I still need to sit down and
write the necessary scripts at some point.
Bug: 5110679
Change-Id: I87e563f0f95aa8e68b45578e2a8f448bbf827a33
