Fixed bugreport:7105 where pierce defense must ignore def and add (def/2) as additional ATK damage.
Fixed bugreport:7148 where r17072 broke the ability of smiths to forge weapons.

git-svn-id: https://rathena.svn.sourceforge.net/svnroot/rathena/trunk@17089 54d463be-8e91-2dee-dedb-b68131a5f0ec