Implement DR482: namespace members can be redeclared with a qualified name

Implement DR482: namespace members can be redeclared with a qualified name
within their namespace, and such a redeclaration isn't required to be a
definition any more.

Update DR status page to say Clang 3.4 instead of SVN and add new Clang 3.5
category (but keep Clang 3.4 yellow for now).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@196481 91177308-0d34-0410-b5e6-96231b3b80d8