ctf_stats: Add ctf_stats.request_save

This functionality allows mods to request a save (not immediate) if they modify player stats.

mods/ctf/ctf_classes/medic.lua

@@ -91,6 +91,8 @@ minetest.override_item("ctf_bandages:bandage", {
 						color = "0x00FF00",
 						value = reward
 					})
+
+					ctf_stats.request_save()
 				end
 			end
 		end