"While true break" optimization pattern

[Mercerenies]

In the course of performing other optimizations (such as, in particular, #26), it is possible to end up with the following

while true:
    if <simple expression>:
        break
    ...

This can be converted into

while !<simple expression>:
    ...

[Mercerenies]

Consider using

(while (if 1 2 3))

as a benchmark, which currently compiles to

while true:
    if !2:
        break
return null

(Note that the substance of the if gets optimized out by other passes, but we can't get rid of the compound while yet; that's what this issue is meant to address)

[Mercerenies]

Also consider

(while (and 1 2))

which currently compiles to

while true:
    var _cond_0 = null
    if !1:
        _cond_0 = false
    else:
        _cond_0 = 2
    if !_cond_0:
        break
return null

But will hopefully become eligible for this optimization after #26 is resolved.