clang-format: Fix regression introduced by r189353.

Before:
  FirstToken->WhitespaceRange.getBegin()
      .getLocWithOffset(First->LastNewlineOffset);

After:
  FirstToken->WhitespaceRange.getBegin().getLocWithOffset(
      First->LastNewlineOffset);

Re-add logic to prevent breaking after an empty set of parentheses.
Basically it seems that calling a function without parameters is more
like navigating along the same object than it is a separate step of a
builder-type call.

We might need to extends this in future to allow "short" parameters that
e.g. are an index accessing a specific element.

llvm-svn: 190126