Improve indentation after breaking at nested name specifiers.

These always represent a continuation and we should increase the ident.

Before:
aaaaaaaaa(aaaaaaaaaaaaaaaaaaaaa::
          aaaaaaaaaaaaaaaaaaaa);

After:
aaaaaaaaa(aaaaaaaaaaaaaaaaaaaaa::
              aaaaaaaaaaaaaaaaaaaa);

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173675 91177308-0d34-0410-b5e6-96231b3b80d8