Update DemangleConfig.h to better mangle LLVM's version.

There's no need for the demangling bits to depend on libc++ internals,
in the same way they don't when compiled as part of LLVM.

git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@359534 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed