[CSM] Add support for positional audio. (#5516)

Fixes parts of #5389.

src/script/lua_api/l_client.h

@@ -65,6 +65,10 @@ class ModApiClient : public ModApiBase
 	// get_meta(pos)
 	static int l_get_meta(lua_State *L);
 
+	static int l_sound_play(lua_State *L);
+
+	static int l_sound_stop(lua_State *L);
+
 public:
 	static void Initialize(lua_State *L, int top);
 };