[Open Assets] Rock Shield 2.0

Just a quick n simple update, now the Rock Shield is... usable.

It uses the regular ol' targetting system from P_LookForEnemies, so you have a radius of 1024 units to attack enemies from. Once you're locked onto an enemy, it launches itself at said enemy, and once the enemy is hit, the rock respawns faster.

Oh, and I also updated it to remove those annoying teleport messages.

Have fun!