tests: factor.

* tests/glr-regression.at, tests/output.at, tests/push.at,
* tests/regression.at, tests/torture.at, tests/actions.at:
Use AT_YYLEX_* and AT_YYERROR_*.

tests/actions.at

@@ -150,14 +150,8 @@ two: { $$.val = 2; } ;
 sum: { printf ("%d\n", $0.val + $-1.val + $-2.val); } ;
 
 %%
-
-static int
-yylex (void)
-{
-  return 0;
-}
-
 ]AT_YYERROR_DEFINE[
+]AT_YYLEX_DEFINE()[
 int
 main (void)
 {