jobstart: Check prg arguments for NULL.
Merge pull request #1471 from splinterofchaos/fix-jobstart

jobstart: Check prg arguments for NULL.
farsi.c: Misc. fixes

- Converted some functions to return bools, and changed their respective
  comments to reflect that.
- Minor fixes to a few comments
arabic.c: Comment fixes

- Use C99 style comments everywhere
- Fix incorrect references to return values