Make hitting with a wielded potion hit you far less

Hitting a monster with a wielded potion of paralysis or sleep
was practically useless, because it almost always also hit you.
Negate the chance and make it depend on your dex.

doc/fixes3-7-0.txt

@@ -990,6 +990,7 @@ no longer override the effect of a new moon by simply carring a lizard corpse
 make explosions burn monster's armor just like they do hero's armor
 make healing and extra healing better by upping the average amount healed
 lifesaving healing amount depends on the consitution
+hitting a monster with a wielded potion hits you far less
 
 
 Fixes to 3.7.0-x Problems that Were Exposed Via git Repository

src/potion.c

@@ -1868,7 +1868,7 @@ potionhit(struct monst *mon, struct obj *obj, int how)
     }
 
     /* Note: potionbreathe() does its own docall() */
-    if ((distance == 0 || (distance < 3 && rn2(5)))
+    if ((distance == 0 || (distance < 3 && !rn2((1+ACURR(A_DEX))/2)))
         && (!breathless(g.youmonst.data) || haseyes(g.youmonst.data)))
         potionbreathe(obj);
     else if (obj->dknown && cansee(tx, ty))