Use REG_EXTENDED for regex matching

The "7 regex" manual page called 'Basic' regular expressions "Obsolete".

It also matches the pcre expressions slightly better.

sslh-main.c

@@ -212,7 +212,7 @@ static void setup_regex_probe(struct proto *p, config_setting_t* probes)
     for (i = 0; i < num_probes; i++) {
         probe_list[i] = malloc(sizeof(*(probe_list[i])));
         expr = config_setting_get_string_elem(probes, i);
-        res = regcomp(probe_list[i], expr, 0);
+        res = regcomp(probe_list[i], expr, REG_EXTENDED);
         if (res) {
             err = malloc(errsize = regerror(res, probe_list[i], NULL, 0));
             regerror(res, probe_list[i], err, errsize);