[ConstantRange] Add urem support

[ConstantRange] Add urem support

Add urem support to ConstantRange, so we can handle in in LVI. This
is an approximate implementation that tries to capture the most useful
conditions: If the LHS is always strictly smaller than the RHS, then
the urem is a no-op and the result is the same as the LHS range.
Otherwise the lower bound is zero and the upper bound is
min(LHSMax, RHSMax - 1).

Differential Revision: https://reviews.llvm.org/D60952

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@359019 91177308-0d34-0410-b5e6-96231b3b80d8