Fix intoasc() in Informix compat lib. This function used to be a noop.

Patch by Michael Paquier

src/interfaces/ecpg/compatlib/informix.c

@@ -666,12 +666,16 @@ dttofmtasc(timestamp * ts, char *output, int str_len, char *fmtstr)
 int
 intoasc(interval * i, char *str)
 {
+	char *tmp;
+
 	errno = 0;
-	str = PGTYPESinterval_to_asc(i);
+	tmp = PGTYPESinterval_to_asc(i);
 
-	if (!str)
+	if (!tmp)
 		return -errno;
 
+	memcpy(str, tmp, strlen(tmp));
+	free(tmp);
 	return 0;
 }