Move external instantiation for __vector_base_common to vector.cpp

Previously the explicit instantiation for this was in locale.cpp,
but that didn't make much sense. This patch creates a new vector.cpp
source file to contain the explicit instantiation.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@305442 91177308-0d34-0410-b5e6-96231b3b80d8

src/vector.cpp

@@ -0,0 +1,16 @@
+//===------------------------- vector.cpp ---------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "vector"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS __vector_base_common<true>;
+
+_LIBCPP_END_NAMESPACE_STD