for CONFIG_LISTEN. This so a module can have custom options in
the listen block. Like all other CONFIG_* options you are supposed
to return 1 if your module handles this option and 0 if not.
From HOOKTYPE_CONFIGTEST you can also return -1 to indicate error
for an option that is handled by the module.
Note that 'cep' is passed, that is the option for the variable
that is being checked, and not the 'ce', the parent of the listen
block. If you want to access the parent, then use ce->ce_prevlevel.
Bram Matthys
ee20160bc3