Make it possible to link against libstdc++ as well as libsupc++ with CMake.

Linking against libstdc++, rather than libsupc++, is probably better
for people who need to link against clients of libstdc++.  Because
libsupc++ is provided only as a static library, its globals are not
shared between the static library and the copy linked into libstdc++.
This has been found to cause at least one test failure.

This also removes a number of symbols which were multiply defined
between libstdc++ and libc++, only when linking with libstdc++.

Differential Revision: http://llvm-reviews.chandlerc.com/D1825

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@192075 91177308-0d34-0410-b5e6-96231b3b80d8

src/new.cpp

@@ -224,6 +224,8 @@ bad_array_new_length::what() const _NOEXCEPT
 
 #endif // _LIBCPPABI_VERSION
 
+#ifndef LIBSTDCXX
+
 void
 __throw_bad_alloc()
 {
@@ -232,4 +234,6 @@ __throw_bad_alloc()
 #endif
 }
 
+#endif // !LIBSTDCXX
+
 }  // std