Limit maximum accepted command string length to 128 (configurable) as done by Tails (https://mailman.boum.org/pipermail/tails-dev/2014-February/005041.html). Thanks to HulaHoop (https://www.whonix.org/forum/index.php?action=profile;u=87) for suggesting this (https://www.whonix.org/forum/index.php/topic,342.0.html).