Fix shift legalization and lowering for big constants.

Summary: If shift amount is a constant value > 64 bit it is handled incorrectly during type legalization and X86 lowering. This patch the type of shift amount argument in function DAGTypeLegalizer::ExpandShiftByConstant from unsigned to APInt.

Reviewers: nadav, majnemer, sanjoy, RKSimon

Subscribers: RKSimon, llvm-commits

Differential Revision: http://reviews.llvm.org/D10767

llvm-svn: 241790