Formatter/ObjC: In dictionary literals, break after ':', not before it.

Before:
  @{ NSFontAttributeNameeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee
     : regularFont, };

Now:
  @{ NSFontAttributeNameeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee :
     regularFont, };

':'s in dictionary literals (and the corresponding {}s) are now marked as
TT_ObjCDictLiteral too, which makes further improvements to dict literal
layout possible.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182716 91177308-0d34-0410-b5e6-96231b3b80d8