resolv: small improvements for debug logging

 - use __func__ instead of the hand-written and often incorrect names
 - fix a few cosmetic issues, such as those ugly ";;" prefixes
 - add some logging around explore_fqdn and explore_numeric
 - change the verbosity of a few messages
 - replace compile-time DBG macro with verbosity checks in DnsProxyListener
 - delete various unused functions in res_debug
 - skip slow res_pquery() if log level is less than VERBOSE

TODO: convert the remaining ALOGx() lines to LOG(x). Leaving this for a
future patch.

Test: as follows:
    adb shell setprop persist.sys.nw_dns_resolver_log DEBUG
    atest reolv_integration_test

Change-Id: I7153f0c75d39d513fa006e0c1e5bf649d47ba154
diff --git a/res_debug.cpp b/res_debug.cpp
index cfd486d..55a919f 100644
--- a/res_debug.cpp
+++ b/res_debug.cpp
@@ -95,6 +95,8 @@
  * IF IBM IS APPRISED OF THE POSSIBILITY OF SUCH DAMAGES.
  */
 
+#define LOG_TAG "res_debug"
+
 #include <sys/param.h>
 #include <sys/socket.h>
 #include <sys/types.h>
@@ -108,7 +110,6 @@
 #include <errno.h>
 #include <math.h>
 #include <netdb.h>
-#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <strings.h>
@@ -122,7 +123,8 @@
     const char* humanname; /* Its fun name, like "mail exchanger" */
 };
 
-/* add a formatted string to a bounded buffer */
+// add a formatted string to a bounded buffer
+// TODO: convert to std::string
 static char* dbprint(char* p, char* end, const char* format, ...) {
     int avail, n;
     va_list args;
@@ -144,6 +146,7 @@
 
     return p;
 }
+
 static void do_section(const res_state statp, ns_msg* handle, ns_sect section, int pflag) {
     int n, sflag, rrnum;
     int buflen = 2048;
@@ -258,8 +261,9 @@
  * Print the contents of a query.
  * This is intended to be primarily a debugging routine.
  */
-
 void res_pquery(const res_state statp, const u_char* msg, int len) {
+    if (!WOULD_LOG(VERBOSE)) return;
+
     ns_msg handle;
     int qdcount, ancount, nscount, arcount;
     u_int opcode, rcode, id;
@@ -301,9 +305,7 @@
         p = dbprint(p, end, ", %s: %d", p_section(ns_s_ns, (int)opcode), nscount);
         p = dbprint(p, end, ", %s: %d", p_section(ns_s_ar, (int)opcode), arcount);
     }
-    if ((!statp->pfcode) || (statp->pfcode & (RES_PRF_HEADX | RES_PRF_HEAD2 | RES_PRF_HEAD1))) {
-        p = dbprint(p, end, " \n");
-    }
+
     LOG(VERBOSE) << temp;
 
     /*
@@ -316,52 +318,6 @@
     if (qdcount == 0 && ancount == 0 && nscount == 0 && arcount == 0) LOG(VERBOSE) << ";;";
 }
 
-const u_char* p_cdnname(const u_char* cp, const u_char* msg, int len, FILE* file) {
-    char name[MAXDNAME];
-    int n;
-
-    if ((n = dn_expand(msg, msg + len, cp, name, (int) sizeof name)) < 0) return (NULL);
-    if (name[0] == '\0')
-        putc('.', file);
-    else
-        fputs(name, file);
-    return (cp + n);
-}
-
-const u_char* p_cdname(const u_char* cp, const u_char* msg, FILE* file) {
-    return (p_cdnname(cp, msg, PACKETSZ, file));
-}
-
-/* Return a fully-qualified domain name from a compressed name (with
-   length supplied).  */
-
-const u_char* p_fqnname(const u_char* cp, const u_char* msg, int msglen, char* name, int namelen) {
-    int n;
-    size_t newlen;
-
-    if ((n = dn_expand(msg, cp + msglen, cp, name, namelen)) < 0) return (NULL);
-    newlen = strlen(name);
-    if (newlen == 0 || name[newlen - 1] != '.') {
-        if ((int) newlen + 1 >= namelen) /* Lack space for final dot */
-            return (NULL);
-        else
-            strcpy(name + newlen, ".");
-    }
-    return (cp + n);
-}
-
-/* XXX:	the rest of these functions need to become length-limited, too. */
-
-const u_char* p_fqname(const u_char* cp, const u_char* msg, FILE* file) {
-    char name[MAXDNAME];
-    const u_char* n;
-
-    n = p_fqnname(cp, msg, MAXCDNAME, name, (int) sizeof name);
-    if (n == NULL) return (NULL);
-    fputs(name, file);
-    return (n);
-}
-
 /*
  * Names of RR classes and qclasses.  Classes and qclasses are the same, except
  * that C_ANY is a qclass but not a class.  (You can ask for records of class