Added gcc option '-Wconversion'

No warnings for standard numerical types. Still pending alternative
numerical types.

lua.c

@@ -185,7 +185,7 @@ static void print_version (void) {
 static void createargtable (lua_State *L, char **argv, int argc, int script) {
   int i, narg;
   narg = argc - (script + 1);  /* number of positive indices */
-  lua_createtable(L, narg, script + 1);
+  lua_createtable(L, cast_uint(narg), cast_uint(script + 1));
   for (i = 0; i < argc; i++) {
     lua_pushstring(L, argv[i]);
     lua_rawseti(L, -2, i - script);