[DAGCombiner] Teach SimplifySetCC SETUGE X, SINTMIN -> SETLT X, 0 and SETULE...

[DAGCombiner] Teach SimplifySetCC SETUGE X, SINTMIN -> SETLT X, 0 and SETULE X, SINTMAX  -> SETGT X, -1.

These aren't the canonical forms we'd get from InstCombine, but
we do have X86 tests for them. Recognizing them is pretty cheap.

While there make use of APInt:isSignedMinValue/isSignedMaxValue
instead of creating a new APInt to compare with. Also use
SelectionDAG::getAllOnesConstant helper to hide the all ones
APInt creation.