Always put a space after ",".

I am not aware of a case where that would be wrong. The specific case I
am fixing are function parameters wrapped in parenthesis (e.g. in
macros).

Before: function(a,(b));
After:  function(a, (b));

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172351 91177308-0d34-0410-b5e6-96231b3b80d8