swift234

Implement logic for operator splitting of unary operators (e.g. !!x).

Given that the fix for this problem is to insert parentheses, and that we're barfing
in name lookup, we don't have enough information to produce a good fixit here:
in this case, we know where to put the ( in, but we don't know where to put in
the ).  Handle this by pointing the caret right to the location of the ( and
make the diagnostic a lot better.  This is much less common than the binary operator
case anyway.