Replaced #ifdef based multiple include guards by #pragma once.

mediachanger/castorrmc/h/Castor_limits.h

mediachanger/castorrmc/h/Cdomainname.h

mediachanger/castorrmc/h/Cglobals.h

mediachanger/castorrmc/h/Cinit.h

mediachanger/castorrmc/h/Cnetdb.h

mediachanger/castorrmc/h/marshall.h

mediachanger/castorrmc/h/net.h

mediachanger/castorrmc/h/osdep.h

mediachanger/castorrmc/h/patchlevel.h.in

mediachanger/castorrmc/h/rbtsubr_constants.h

mediachanger/castorrmc/h/rmc_api.h

mediachanger/castorrmc/h/rmc_constants.h

mediachanger/castorrmc/h/rmc_find_char.h

mediachanger/castorrmc/h/rmc_get_acs_drive_id.h

mediachanger/castorrmc/h/rmc_get_loader_type.h

mediachanger/castorrmc/h/rmc_get_rmc_host_of_drive.h

mediachanger/castorrmc/h/rmc_logit.h

mediachanger/castorrmc/h/rmc_logreq.h

mediachanger/castorrmc/h/rmc_marshall_element.h

mediachanger/castorrmc/h/rmc_procreq.h