- Changed itemhealrate to itemgrouphealrate, added a structure itemhealrate to allow storing item-healing bonuses per item.
- Modified bAddItemHealRate so it can receive both item-id and item-group values (since the first item-id is +500, there's no risk of mixing them up).
git-svn-id: https://svn.code.sf.net/p/rathena/svn/trunk@8136 54d463be-8e91-2dee-dedb-b68131a5f0ec