Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

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

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

Import jemalloc 37b6f95dcd866f51c91488531a2efc3ed4c2b754 (dev branch,
prior to 3.0.0 release). This version is likely very close to what will be
3.0.0.

Import jemalloc b57d3ec571c6551231be62b7bf92c084a8c8291c (dev branch,
prior to 3.0.0 release), which supports atomic operations based on atomic(9).
This should fix build failures for several platforms.

Import jemalloc 9ef7f5dc34ff02f50d401e41c8d9a4a928e7c2aa (dev branch,
prior to 3.0.0 release) as contrib/jemalloc, and integrate it into libc.
The code being imported by this commit diverged from
lib/libc/stdlib/malloc.c in March 2010, which means that a portion of
the jemalloc 1.0.0 ChangeLog entries are relevant, as are the entries
for all subsequent releases.