Add libgmp 6.2.0 to third_party

Don't build it yet.  That will come in the next review.

Change-Id: Idf3266558165e5ab45f4a41c98cc8c838c8244d5
diff --git a/third_party/gmp/mpn/vax/lshift.asm b/third_party/gmp/mpn/vax/lshift.asm
new file mode 100644
index 0000000..941e999
--- /dev/null
+++ b/third_party/gmp/mpn/vax/lshift.asm
@@ -0,0 +1,59 @@
+dnl  VAX mpn_lshift -- left shift.
+
+dnl  Copyright 1999-2001, 2012 Free Software Foundation, Inc.
+
+dnl  This file is part of the GNU MP Library.
+dnl
+dnl  The GNU MP Library is free software; you can redistribute it and/or modify
+dnl  it under the terms of either:
+dnl
+dnl    * the GNU Lesser General Public License as published by the Free
+dnl      Software Foundation; either version 3 of the License, or (at your
+dnl      option) any later version.
+dnl
+dnl  or
+dnl
+dnl    * the GNU General Public License as published by the Free Software
+dnl      Foundation; either version 2 of the License, or (at your option) any
+dnl      later version.
+dnl
+dnl  or both in parallel, as here.
+dnl
+dnl  The GNU MP Library is distributed in the hope that it will be useful, but
+dnl  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+dnl  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+dnl  for more details.
+dnl
+dnl  You should have received copies of the GNU General Public License and the
+dnl  GNU Lesser General Public License along with the GNU MP Library.  If not,
+dnl  see https://www.gnu.org/licenses/.
+
+include(`../config.m4')
+
+ASM_START()
+PROLOGUE(mpn_lshift)
+	.word	0x1c0
+	movl	4(ap), r7
+	movl	8(ap), r6
+	movl	12(ap), r1
+	movl	16(ap), r8
+
+	moval	(r6)[r1], r6
+	moval	(r7)[r1], r7
+	clrl	r3
+	movl	-(r6), r2
+	ashq	r8, r2, r4
+	movl	r5, r0
+	movl	r2, r3
+	decl	r1
+	jeql	L(end)
+
+L(top):	movl	-(r6), r2
+	ashq	r8, r2, r4
+	movl	r5, -(r7)
+	movl	r2, r3
+	sobgtr	r1, L(top)
+
+L(end):	movl	r4, -4(r7)
+	ret
+EPILOGUE()