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/mp_dv_tab.c b/third_party/gmp/mp_dv_tab.c
new file mode 100644
index 0000000..cd09d5d
--- /dev/null
+++ b/third_party/gmp/mp_dv_tab.c
@@ -0,0 +1,77 @@
+/* __gmp_digit_value_tab -- support for mp*_set_str
+
+   THE CONTENTS OF THIS FILE ARE FOR INTERNAL USE AND MAY CHANGE
+   INCOMPATIBLY OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
+
+Copyright 2003, 2013 Free Software Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP Library is free software; you can redistribute it and/or modify
+it under the terms of either:
+
+  * the GNU Lesser General Public License as published by the Free
+    Software Foundation; either version 3 of the License, or (at your
+    option) any later version.
+
+or
+
+  * the GNU General Public License as published by the Free Software
+    Foundation; either version 2 of the License, or (at your option) any
+    later version.
+
+or both in parallel, as here.
+
+The GNU MP Library is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received copies of the GNU General Public License and the
+GNU Lesser General Public License along with the GNU MP Library.  If not,
+see https://www.gnu.org/licenses/.  */
+
+#include "gmp-impl.h"
+
+/* Table to be indexed by character, to get its numerical value.  Assumes ASCII
+   character set.
+
+   First part of table supports common usages, where 'A' and 'a' have the same
+   value; this supports bases 2..36
+
+   At offset 208, values for bases 37..62 start.  Here, 'A' has the value 10
+   (in decimal) and 'a' has the value 36.  */
+
+#define X 0xff
+const unsigned char __gmp_digit_value_tab[] =
+{
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,
+  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, X, X, X, X, X, X,
+  X,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,
+  25,26,27,28,29,30,31,32,33,34,35,X, X, X, X, X,
+  X,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,
+  25,26,27,28,29,30,31,32,33,34,35,X, X, X, X, X,
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,
+  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, X, X, X, X, X, X,
+  X,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,
+  25,26,27,28,29,30,31,32,33,34,35,X, X, X, X, X,
+  X,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,
+  51,52,53,54,55,56,57,58,59,60,61,X, X, X, X, X,
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,
+  X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X
+};