Do not rely on the underlying type of time_t in date(1) and touch(1)

Use LLONG_MAX unconditionally.  In practice this only causes trouble
with systems that are not 2038 ready.

date.c

@@ -26,7 +26,7 @@ main(int argc, char *argv[])
 	t = time(NULL);
 	ARGBEGIN {
 	case 'd':
-		t = estrtonum(EARGF(usage()), 0, MIN(LLONG_MAX, (time_t)-1));
+		t = estrtonum(EARGF(usage()), 0, LLONG_MAX);
 		break;
 	case 'u':
 		tztime = gmtime;

touch.c

@@ -73,7 +73,7 @@ main(int argc, char *argv[])
 		t = st.st_mtime;
 		break;
 	case 't':
-		t = estrtonum(EARGF(usage()), 0, MIN(LLONG_MAX, (time_t)-1));
+		t = estrtonum(EARGF(usage()), 0, LLONG_MAX);
 		break;
 	default:
 		usage();