Switch to chainsaw when starting new level

If the player has a chainsaw and a berserk power-up, and ends a level
with their fists selected, they start the next level with their fists.
This shouldn't happen, because the berserk power-up has been removed and
they have the chainsaw. This commit corrects this. Thanks to @plumsinus
for finding this!

src/g_game.c

@@ -1019,6 +1019,9 @@ void G_PlayerFinishLevel(int player)
     p->fixedcolormap = 0;               // cancel ir gogles
     p->damagecount = 0;                 // no palette changes
     p->bonuscount = 0;
+
+    if (p->readyweapon == wp_fist && p->weaponowned[wp_chainsaw])
+        p->readyweapon = wp_chainsaw;
 }
 
 //