Unallowed cases are now handled in devices.cc and cause a BX_ERROR.
- io_len mask fixed and unnecessary io_len checks removed in
* devices.cc
* extfpuirq.cc
* gameport.cc
* ne2k.cc
* pit.cc
* pit_wrap.cc (i/o register function calls replaced by DEV_* macro calls)
- TODO: implement this in all other devices