Initial support for formatting ObjC method declarations/calls.

We can now format stuff like:
- (void)doSomethingWith:(GTMFoo *)theFoo
                   rect:(NSRect)theRect
               interval:(float)theInterval {
  [myObject doFooWith:arg1 //
                 name:arg2
                error:arg3];

}

This seems to fix everything mentioned in llvm.org/PR14939.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@174364 91177308-0d34-0410-b5e6-96231b3b80d8