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: r253266

Prefix the alias macros for members of struct __mcontext with an underscore
in order to avoid a clash in the net80211 code.

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

Approved by: re (implicit)

Implement

Reviewed by: marcel
Approved by: re (kib)
MFC after: 1 week

Cleanup for WARNS 6.

Cleanup for WARNS 3.

Correct the mess I made by committing from the wrong tree. Most
notably, this restores some of the contents in thread_db.h as well
as David Xu's copyright notice. This also fixes the includes in
the MD libpthread files which Scott tried to provide a quick fix
for.

Pointy hat: marcel

Add missing #includes so that this can compile. Obtained from the i386 version.

Add rudimentary support and stubs for libthr and libc_r on alpha, amd64,
i386, ia64 and sparc64. Add stubs for alpha, amd64, ia64 and sparc64 for
libpthread.

Restructure the source files to avoid unnecessary use of subdirectories
that also force us to use non-portable compilation flags to deal with
the uncommon compilation requirements (building archive libraries for
linkage into a shared library).

The libpthread support has been copied from the original local and
cleaned-up to make them WARNS=2 clean.
that also force us to use non-portable compilation flags to deal with
the uncommon compilation requirements (building archive libraries for
linkage into a shared library).

The libpthread support has been copied from the original local and
cleaned-up to make them WARNS=2 clean.

Tested on: amd64, i386, ia64