MachineRegionInfo.cpp: Another fix on MachineRegionInfo::MachineRegionInfo::recalculate() to appease msc17.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213476 91177308-0d34-0410-b5e6-96231b3b80d8
SIISelLowering.cpp: Define _USE_MATH_DEFINES to let M_PI provided on MS <cmath>.

FIXME: Would it be better to move it into configure?

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213477 91177308-0d34-0410-b5e6-96231b3b80d8