Make illegal casts throw exception.

lib/master.pike.in

lib/modules/ADT.pmod/Interval.pike

lib/modules/ADT.pmod/Queue.pike

lib/modules/ADT.pmod/Relation.pmod/Binary.pike

lib/modules/ADT.pmod/Set.pike

lib/modules/ADT.pmod/Stack.pike

lib/modules/ADT.pmod/Struct.pike

lib/modules/ADT.pmod/Table.pmod

lib/modules/Calendar.pmod/Event.pmod

lib/modules/GLUE.pmod/Events.pmod

lib/modules/Geography.pmod/Countries.pmod

lib/modules/Geography.pmod/Position.pike

lib/modules/Int.pmod

lib/modules/Locale.pmod/module.pmod

lib/modules/MIME.pmod/ext_to_media_type.pmod

lib/modules/MIME.pmod/module.pmod

lib/modules/Mapping.pmod

lib/modules/NetUtils.pmod

lib/modules/Parser.pmod/C.pmod

lib/modules/Parser.pmod/LR.pmod/module.pmod