clang-format: Don't indent relative to ./->.

Before:
  SomeThing          // break
      .SomeFunction( // break
           param);
After:
  SomeThing          // break
      .SomeFunction( // break
          param);

Seems to be more common in editors and codebases I have looked at.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@199105 91177308-0d34-0410-b5e6-96231b3b80d8