Move the adb auth code into its own file.

Change-Id: I84cf0bd7777f0147119e7c6afc4096c2e93156a2
diff --git a/adb/adb.h b/adb/adb.h
index 600bdd5..48f2a25 100644
--- a/adb/adb.h
+++ b/adb/adb.h
@@ -424,6 +424,11 @@
 int sendfailmsg(int fd, const char *reason);
 int handle_host_request(char *service, transport_type ttype, char* serial, int reply_fd, asocket *s);
 
+void handle_online(atransport *t);
+void handle_offline(atransport *t);
+
+void send_connect(atransport *t);
+
 #ifdef __cplusplus
 }
 #endif