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/printf/fprintf.c b/third_party/gmp/printf/fprintf.c
new file mode 100644
index 0000000..0008b3b
--- /dev/null
+++ b/third_party/gmp/printf/fprintf.c
@@ -0,0 +1,48 @@
+/* gmp_fprintf -- formatted output.
+
+Copyright 2001 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 <stdarg.h>
+#include <stdio.h>
+
+#include "gmp-impl.h"
+
+
+int
+gmp_fprintf (FILE *fp, const char *fmt, ...)
+{
+  va_list  ap;
+  int      ret;
+
+  va_start (ap, fmt);
+
+  ret = __gmp_doprnt (&__gmp_fprintf_funs, fp, fmt, ap);
+  va_end (ap);
+  return ret;
+}