Update 0.8.84

Split-screen can be switched to horizontal/vertical in the main menu.
Additional optimization on the levels Abandoned Cliff, Castle, RLS, Aircraft Factory, Elysium 3.
The character sometimes reacts to pain with a voice. The voice is the same as when the player is hit by a sniper bullet and thrown back.
Fixed a critical bug on the desert level, which occurs in a cooperative game if the second player is male.