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 r261080:
The posix_fallocate(2) syscall should return error number on error,
without modifying errno.

MFC r261290:
The posix_madvise(3) and posix_fadvise(2) should return error on
failure, same as posix_fallocate(2).

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Add the POSIX 1003.1-2001 posix_madvise() interface.

PR: standards/54634
Reviewed by: das
Approved by: jake (mentor)

Fix SCM ID's.

Add a couple of new library interfaces (will be activated when the
relavant header file changes are committed) for POSIX support.