Fix failing tests in bash mode

[BolunThompson]

The new bash parser is experimental — many of the bash interface tests aren’t run because they fail. It would be good if these were fixed.

Notes:

1. The goal is for pash to compile the tests without crashing. These are generally not parallelizable, which is ok.
2. Some of these already work due to intermediate changes, but haven’t been uncommented.

[BolunThompson]

An interesting case is arithmetic for loops. These don’t run correctly but (I think) should be parallelizable even without any other logical changes to pash. Example failing script:

#!/bin/bash

for (( x=0; x < 3; ++x )); do
  grep done "$0"
done