Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC 246120,246148,246206,246587,247411,247415:
Add fmemopen(3), open_memstream(3), and open_wmemstream(3) which provide
stdio FILE objects for memory buffers.

port exprun by: bdrewery

Add fmemopen(3), an interface to get a FILE * from a buffer in memory, along
with the respective regression test.
See http://pubs.opengroup.org/onlinepubs/9699919799/functions/fmemopen.html

Reviewed by: cognet
Approved by: cognet