dns-query: export CNAME_MAX, so that we can use it in other files, too

Let's rename it a bit, to be more explanatory while exporting it.

(And let's bump the CNAME limit to 16 — 8 just sounded so little)

src/resolve/resolved-dns-query.c

@@ -10,7 +10,6 @@
 #include "resolved-etc-hosts.h"
 #include "string-util.h"
 
-#define CNAME_MAX 8
 #define QUERIES_MAX 2048
 #define AUXILIARY_QUERIES_MAX 64
 
@@ -977,7 +976,7 @@ static int dns_query_cname_redirect(DnsQuery *q, const DnsResourceRecord *cname)
         assert(q);
 
         q->n_cname_redirects++;
-        if (q->n_cname_redirects > CNAME_MAX)
+        if (q->n_cname_redirects > CNAME_REDIRECT_MAX)
                 return -ELOOP;
 
         r = dns_question_cname_redirect(q->question_idna, cname, &nq_idna);

src/resolve/resolved-dns-query.h

@@ -145,3 +145,5 @@ static inline uint64_t dns_query_reply_flags_make(DnsQuery *q) {
                                       dns_query_fully_confidential(q)) |
                 (q->answer_query_flags & (SD_RESOLVED_FROM_MASK|SD_RESOLVED_SYNTHETIC));
 }
+
+#define CNAME_REDIRECT_MAX 16