G_CoopGametype, for all the GT_COOP cases

src/d_netcmd.c

src/g_game.c

src/g_game.h

src/hu_stuff.c

src/lua_baselib.c

src/p_inter.c

src/p_mobj.c

src/p_spec.c

src/p_user.c

src/st_stuff.c