Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Remove unneeded mappings from libmap32.conf. Move it up one level and
install it on powerpc64 in addition to amd64.

Reviewed by: kib
Approved by: re (blanket)

Add a stock libmap32.conf for amd64. The first two lines have no effect
except to document the hardcoded standard library search path for 32-bit
binaries. The third line performs the equivalent substitution for the
private library directory.

Ironically, these entries rely on functionality which is only available
in the COMPAT_32BIT version of rtld-elf.

Approved by: re (blanket)