Improvements in the handling of signals

Added 'volatile' to 'l_signalT' variables plus some minor changes.

lua.c

@@ -54,8 +54,9 @@ static void lstop (lua_State *L, lua_Debug *ar) {
 ** interpreter.
 */
 static void laction (int i) {
+  int flag = LUA_MASKCALL | LUA_MASKRET | LUA_MASKLINE | LUA_MASKCOUNT;
   signal(i, SIG_DFL); /* if another SIGINT happens, terminate process */
-  lua_sethook(globalL, lstop, LUA_MASKCALL | LUA_MASKRET | LUA_MASKCOUNT, 1);
+  lua_sethook(globalL, lstop, flag, 1);
 }