clang-format: Fix bug with comments between non-trival parameters.

Before:
  SomeFunction(a, a,
               // comment
                      b + x);

After:
  SomeFunction(a, a,
               // comment
               b + x);

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@219209 91177308-0d34-0410-b5e6-96231b3b80d8