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

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

Add a test for number of CPUs configured/online.

MFC after: 1 week

Add simple test to check the functioning of retrieval of
pagesize()/pagesizes() after change to use aux vector. Note that
public function getosreldate() is different from libc-internal
__getosreldate() and does not use aux to fetch osreldate value.

MFC after: 1 month