Add program to double-check VEX constant folding. BZ 506211

Add program to double-check VEX constant folding. BZ 506211

Using IR injection. Essentially:
- prepare input values for an IROp
- create an IRExpr for the IRop
- constant fold the expression
- make sure the result is an IRConst with the expected value

Only IROps with integer operands and result are supported.
No vector and floating point IROps. Maximum bit width is 64.

Part of fixing https://bugs.kde.org/show_bug.cgi?id=506211