Iron bars can be dissolved by potions of acid.

git-svn-id: https://unnethack.svn.sourceforge.net/svnroot/unnethack/trunk@1411 f1e491ac-5ded-4967-80bf-9f4855be876a
Give acid breath a chance of dissolving iron bars

git-svn-id: https://unnethack.svn.sourceforge.net/svnroot/unnethack/trunk@1412 f1e491ac-5ded-4967-80bf-9f4855be876a
Update ChangeLog: Blasts or thrown potions of acid destroy iron bars


git-svn-id: https://unnethack.svn.sourceforge.net/svnroot/unnethack/trunk@1413 f1e491ac-5ded-4967-80bf-9f4855be876a