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/demos/perl/test2.pl b/third_party/gmp/demos/perl/test2.pl
new file mode 100644
index 0000000..31a1d6b
--- /dev/null
+++ b/third_party/gmp/demos/perl/test2.pl
@@ -0,0 +1,75 @@
+# GMP perl module tests (part 2)
+
+# 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/.
+
+
+# The following uses of :constants seem to provoke segvs in perl 5.005_03,
+# so they're kept separate file to be run only on suitable perl versions.
+
+
+use GMP::Mpz qw(:constants);
+{
+  my $a = 123;
+  ok (UNIVERSAL::isa ($a, "GMP::Mpz"));
+}
+use GMP::Mpz qw(:noconstants);
+
+use GMP::Mpq qw(:constants);
+{
+  my $a = 123;
+  ok (UNIVERSAL::isa ($a, "GMP::Mpq"));
+}
+use GMP::Mpq qw(:noconstants);
+
+use GMP::Mpf qw(:constants);
+{
+  my $a = 123;
+  ok (UNIVERSAL::isa ($a, "GMP::Mpf"));
+}
+use GMP::Mpf qw(:noconstants);
+
+
+# compiled constants unchanged by clrbit etc when re-executed
+foreach (0, 1, 2) {
+  use GMP::Mpz qw(:constants);
+  my $a = 15;
+  my $b = 6;
+  use GMP::Mpz qw(:noconstants);
+  clrbit ($a, 0);
+  ok ($a == 14);
+  setbit ($b, 0);
+  ok ($b == 7);
+}
+
+1;
+
+
+# Local variables:
+# perl-indent-level: 2
+# End: