Drop old logic which allowed to have only a rigportnumber

- RIGPORT expects a whole portname (e.g. /dev/ttyS0")
disabling rig control if no hamlib library compiled in
drop init_ and close_ function for native_rig
drop unneeded native_rig_get_mode()
drop native_rig_reset_rit()
drop all calls to native_rig_ functions from gettxinfo()
drop all remaining native_rig_ functions
cleanup header files and add include guards