fix typo

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@171916 91177308-0d34-0410-b5e6-96231b3b80d8
add extra namespace for gcc-4.7 compatibility

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@171918 91177308-0d34-0410-b5e6-96231b3b80d8