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/arm/rshift.asm b/third_party/gmp/mpn/arm/rshift.asm
new file mode 100644
index 0000000..9ddbc2e
--- /dev/null
+++ b/third_party/gmp/mpn/arm/rshift.asm
@@ -0,0 +1,86 @@
+dnl  ARM mpn_rshift.
+
+dnl  Contributed to the GNU project by Torbjörn Granlund.
+
+dnl  Copyright 1997, 2000, 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')
+
+C	     cycles/limb
+C StrongARM	 ?
+C XScale	 ?
+C Cortex-A7	 ?
+C Cortex-A8	 ?
+C Cortex-A9	 3.5
+C Cortex-A15	 ?
+
+define(`rp',  `r0')
+define(`up',  `r1')
+define(`n',   `r2')
+define(`cnt', `r3')
+define(`tnc', `r12')
+
+ASM_START()
+PROLOGUE(mpn_rshift)
+	push	{r4, r6, r7, r8}
+	ldr	r4, [up]
+	rsb	tnc, cnt, #32
+
+	mov	r7, r4, lsr cnt
+	tst	n, #1
+	beq	L(evn)			C n even
+
+L(odd):	subs	n, n, #2
+	bcc	L(1)			C n = 1
+	ldr	r8, [up, #4]!
+	b	L(mid)
+
+L(evn):	ldr	r6, [up, #4]!
+	subs	n, n, #2
+	beq	L(end)
+
+L(top):	ldr	r8, [up, #4]!
+	orr	r7, r7, r6, lsl tnc
+	str	r7, [rp], #4
+	mov	r7, r6, lsr cnt
+L(mid):	ldr	r6, [up, #4]!
+	orr	r7, r7, r8, lsl tnc
+	str	r7, [rp], #4
+	mov	r7, r8, lsr cnt
+	subs	n, n, #2
+	bgt	L(top)
+
+L(end):	orr	r7, r7, r6, lsl tnc
+	str	r7, [rp], #4
+	mov	r7, r6, lsr cnt
+L(1):	str	r7, [rp]
+	mov	r0, r4, lsl tnc
+	pop	{r4, r6, r7, r8}
+	return	r14
+EPILOGUE()