Before passing a command to a command handler the quotes are stripped
from each argument in the command. This is usually the wanted behavior
but causes a problem in the case of `exec` where quoted arguments can be
required when passing the exec command to `/bin/sh -c`.
This patch makes `exec` a special case and doesn't strip quotes from the
arguments. It will just pass the exec command verbatim to the exec
command handler.
Fix#518
99f26c61a5