[PATCH] Contribute FreeBSD unwind support (x86_64 and x86)

[John Marino <gnugcc at marino dot st>]

I have maintained unwind support for FreeBSD i386 and x86_64 in my
"gnat-aux" repository for many years (I created it).  I've always
intended on contributing it back to GCC, but I never got around to
"proving" it worked until now.

The version I've been using actually has two flavors: FreeBSD 8 and
below and FreeBSD 9 and above.  However, the last of the FreeBSD 8
releases reaches EOL at the end of June so the unwind support I've
attached here drops the FreeBSD 8 variation for simplicity's sake.

I was under the impression that MD unwinding was used for more than just
GNAT but it looks like that impression was wrong.  When I ran the
testsuite, the only tests affected were Ada tests.

FreeBSD 10.1 / gcc-6.0.0 before patch applied:
http://leaf.dragonflybsd.org/~marino/freebsd/summary-100F64.txt

FreeBSD 10.1 / gcc-6.0.0 after patch applied:
http://leaf.dragonflybsd.org/~marino/freebsd/summary-unwind-100F64.txt

Difference between runs:
http://leaf.dragonflybsd.org/~marino/freebsd/unwind-diff-100F64.txt

FreeBSD 11/amd64 with patch (Ada only):
http://leaf.dragonflybsd.org/~marino/freebsd/summary-110F64.txt

FreeBSD 11/i386 with patch (Ada only)
http://leaf.dragonflybsd.org/~marino/freebsd/summary-110F32.txt


Note that I provided a similar unwind support for DragonFly a few months
ago.  Please consider applying the attached patch to gcc trunk.   (copy
of patch found here:
http://leaf.dragonflybsd.org/~marino/freebsd/freebsd-unwind-support.diff )

Suggested text for libgcc/ChangeLog:

2015-05-XX  John Marino <gnugcc@marino.st>

	* config.host (i[34567]86-*-freebsd*, x86_64-*-freebsd*):
	Set md_unwind_header
	* config/i386/freebsd-unwind.h: New.


Also please recall that my copyright assignment to FSF is in order!
Thanks,
John Marino

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