Add test to ensure that iterator_traits<NotAnIterator> doesn't have a value type

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@224295 91177308-0d34-0410-b5e6-96231b3b80d8
Fix the literal string that I said would be six elements long to actually be six elements long. Octal. Sheesh.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@224297 91177308-0d34-0410-b5e6-96231b3b80d8
Once more w/o the typo.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@224298 91177308-0d34-0410-b5e6-96231b3b80d8
Fix installheaders target's permissions

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@224300 91177308-0d34-0410-b5e6-96231b3b80d8