[libc++] Don't hardcode namespace in manual mangling

libc++'s inline namespace can change depending on the ABI version.
Instead of hardcoding __1 in the manual Microsoft ABI manglings for the
iostream globals, stringify _LIBCPP_NAMESPACE and use that instead, to
work across all ABI versions.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@310290 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed