Lift trivial Ifs

[ThrudPrimrose]

Dead control flow elimination does not simplify by trying to evaluate trivial if conditions. I wrote a pass that does that:

It tries to eval if branches that are trivially true and then lifts the inner CFG upwards: Becomes:

It supports branches of type:

if (cond)

and (empty else):

if(cond) 
...
else:
....

Example: Becomes:

[phschaad]

Pinging @tbennun for re-review about the mentioned minor change