Add the missing 'LoopToScev' parameter

Contributed-by: Yabin Hu <yabin.hwu@gmail.com>
Remove unnecessary explicit typing in std::make_pair

Contributed-by: Yabin Hu <yabin.hwu@gmail.com>
Replace llvm::IRBuilder with PollyIRBuilder

Contributed-by:  Yabin Hu <yabin.hwu@gmail.com>