async resolvers: further cleanups

asyn-ares.c and asyn-thread.c are two separate backends that implement
the same (internal) async resolver API for libcurl to use. Backend is
specified at build time.

The internal resolver API is defined in asyn.h for asynch resolvers.

lib/hostasyn.c

@@ -127,4 +127,43 @@ CURLcode Curl_addrinfo_callback(struct connectdata *conn,
   return rc;
 }
 
+/* Call this function after Curl_connect() has returned async=TRUE and
+   then a successful name resolve has been received.
+
+   Note: this function disconnects and frees the conn data in case of
+   resolve failure */
+CURLcode Curl_async_resolved(struct connectdata *conn,
+                             bool *protocol_done)
+{
+  CURLcode code;
+
+  if(conn->async.dns) {
+    conn->dns_entry = conn->async.dns;
+    conn->async.dns = NULL;
+  }
+
+  code = Curl_setup_conn(conn, protocol_done);
+
+  if(code)
+    /* We're not allowed to return failure with memory left allocated
+       in the connectdata struct, free those here */
+    Curl_disconnect(conn, FALSE); /* close the connection */
+
+  return code;
+}
+
+/*
+ * Curl_getaddrinfo() is the generic low-level name resolve API within this
+ * source file. There are several versions of this function - for different
+ * name resolve layers (selected at build-time). They all take this same set
+ * of arguments
+ */
+Curl_addrinfo *Curl_getaddrinfo(struct connectdata *conn,
+                                const char *hostname,
+                                int port,
+                                int *waitp)
+{
+  return Curl_resolver_getaddrinfo(conn, hostname, port, waitp);
+}
+
 #endif /* CURLRES_ASYNCH */