Fix regression from r259622: the operand of an increment that is the operand of

a cast expression is not the operand of a cast expression itself, so if it's
parenthesized we need to form a ParenExpr not a ParenListExpr.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@259677 91177308-0d34-0410-b5e6-96231b3b80d8