adb: switch apacket over to a std::string payload.

Test: python test_device.py with walleye/x86_64 emulator
Change-Id: I0a18941af1cb2279e5019a24ace25741def1202f
diff --git a/adb/adb_auth.h b/adb/adb_auth.h
index a6f224f..715e04f 100644
--- a/adb/adb_auth.h
+++ b/adb/adb_auth.h
@@ -49,7 +49,7 @@
 void adbd_auth_verified(atransport *t);
 
 void adbd_cloexec_auth_socket();
-bool adbd_auth_verify(const char* token, size_t token_size, const char* sig, int sig_len);
+bool adbd_auth_verify(const char* token, size_t token_size, const std::string& sig);
 void adbd_auth_confirm_key(const char* data, size_t len, atransport* t);
 
 void send_auth_request(atransport *t);