parse_c: update incomplete type handling: make auto_predeclare_unknown_structs the default w/o warning, remove the associated pragma
parse_c: update incomplete type handling: make auto_predeclare_unknown_structs the default w/o warning, remove the associated pragma

chubbymaggie/metasm,rapid7/metasm,w4kfu/metasm,CBongo/metasm,jjyg/metasm