Help commands segmentation faults

[Lukáš Zaoral]

Hello,
unfortunately, the issue #79 wasn't fully fixed. Divine still crashes in these cases:

1) Query for an unknown command, both with divine help or in sim environment with help command.

2) divine help version

3) In sim environment with following commands help {up,down,set,exit}

Thanks.

[mornfall]

Hopefully fixed all the problems now. I have added the cases that you describe to a regression test.