Add gmock into our dependencies.

third_party/boost/boost/config/abi_prefix.hpp

Index: third_party/boost/boost/config/abi_prefix.hpp
diff --git a/third_party/boost/boost/config/abi_prefix.hpp b/third_party/boost/boost/config/abi_prefix.hpp
new file mode 100644
index 0000000000000000000000000000000000000000..3b1347492cab03c0491345bffe8b1c25193f7390
--- /dev/null
+++ b/third_party/boost/boost/config/abi_prefix.hpp
@@ -0,0 +1,25 @@
+//  abi_prefix header  -------------------------------------------------------//
+
+// (c) Copyright John Maddock 2003
+   
+// Use, modification and distribution are subject to the Boost Software License,
+// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt).
+
+#ifndef BOOST_CONFIG_ABI_PREFIX_HPP
+# define BOOST_CONFIG_ABI_PREFIX_HPP
+#else
+# error double inclusion of header boost/config/abi_prefix.hpp is an error
+#endif
+
+#include <boost/config.hpp>
+
+// this must occur after all other includes and before any code appears:
+#ifdef BOOST_HAS_ABI_HEADERS
+#  include BOOST_ABI_PREFIX
+#endif
+
+#if defined( __BORLANDC__ )
+#pragma nopushoptwarn
+#endif
+