tls: in AES-GCM decoding, avoid memmove

function                                             old     new   delta
xorbuf3                                                -      36     +36
xorbuf                                                24      12     -12
tls_xread_record                                     656     634     -22
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/2 up/down: 36/-34)              Total: 2 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/networking/tls.h b/networking/tls.h
index f2ef67a..4b0dc74 100644
--- a/networking/tls.h
+++ b/networking/tls.h
@@ -81,6 +81,7 @@
 #define AES_BLOCK_SIZE  16
 
 void tls_get_random(void *buf, unsigned len) FAST_FUNC;
+void xorbuf(void* buf, const void* mask, unsigned count) FAST_FUNC;
 
 #define matrixCryptoGetPrngData(buf, len, userPtr) (tls_get_random(buf, len), PS_SUCCESS)