TODO

Immediate:
- Implement WHILE/UNTIL loop, minus CONTINUE/BREAK.
   - Similar concept to IF, just IF is repeatedly inserted back into the
     accessor queue.
   * i)  Parse
     ii) Process
- Free command sturcture after command finishes.

Long term:
- The variables hash is implemented. Use it. This includes
   i)  Parse variable assignments/use.
   ii) On variable use, replace variable with value.
- Once we have variables, implement FOR.
- Once we have both WHILE and FOR, it'd be good to implement CONTINUE and BREAK.

Super long term:
Worry about subshells. When working with modifying Dash, this proved to be
kind of a wall. Get around that wall.

Less important:
- Optimize IF:
   Right now either THEN or ELSE is inserted after evaluating the CONDITION.
   If a subpart of the CONDITION evaluates to true, immediately insert the
   THEN portion.
- Make IF more flexible: right now, both THEN and ELSE portions are required.
  Technically only THEN portion is required.
- Implement ELIF.

Bugs:
- Noticed this when running make inside Parsh: Bash knows where stdbool.h is.
  Parsh doesn't. Maybe add something to path?