Adds a three-second cooldown to the alien hunter pounce

Does as the name implies. I was inspired to make this after a round on Sybil in which one alien hunter knocked down an entire deathsquad. Pounce is still viable, but far less spammy.

In addition, you are put out of leap mode as soon as you land. Since you can no longer leap many times consecutively, there would only be dead time in turning off leap mode.
Feel free to look at the code for the main leap toggle button, since I myself wasn't great at HUD buttons.

(also, as for toggle_no_msg() or what ho, just make it an agrument to the first proc, defaulting to playing the message)