Commit more accepted upstream changes from <NetBSD>/tests/...
This includes a number of accepted patches for:
- lib/libc/sys
- lib/libm
christos was also nice enough to do the heavy lifting with the h_macros.h
#includes so testcases which use h_macros.h now can work more easily with
the FreeBSD tree's layout for contrib/netbsd-tests vs the testcases.