[Valgrind-developers] ir_opt.c tweaks

[Florian K. <fl...@ei...>]

I was doing some tests with --vex-iropt-verbosity and noticed a
few unhandled cases in constant folding. The patch below fixes
those. There are more tweaks that could possibly be added to
constant folding but I did not attempt that.
Added new functions mkFalse and mkTrue for readability.

Regtested on amd64 and s390x with no differences.

OK?

   Florian