Implemented a flagged items database for item groups and Dead Branch type item checks. Credits to @cydh!
Merge branch 'rathena/master'

Conflicts Resolved:
	conf/msg_conf/map_msg.conf
	db/import-tmpl/item_flag.txt
	db/pre-re/item_flag.txt
	db/re/item_flag.txt
	src/map/itemdb.c
	src/map/pc.c

Signed-off-by: Cydh Ramdh <house.bad@gmail.com>