Fix encode2047 test.

* mailbox/base64.c (_base64_encoder): Fix the use
of uninitialized variable.
* mailbox/rfc2047.c (mu_rfc2047_encode): Rewind the
input stream before reading from it.

@@ -197,7 +197,7 @@ _base64_encoder (void *xd MU_ARG_UNUSED,
       break;
     }
   
-  if (isize <= 3)
+  if (iobuf->isize <= 3)
     {
       if (cmd == mu_filter_lastbuf)
 	pad = 1;

@@ -271,7 +271,7 @@ mu_rfc2047_encode (const char *charset, const char *encoding,
     return rc;
   
   mu_stream_write (input_stream, text, strlen (text), NULL);
-
+  mu_stream_seek (input_stream, 0, MU_SEEK_SET, NULL);
   rc = mu_filter_create (&output_stream, input_stream,
 			 encoding, MU_FILTER_ENCODE, MU_STREAM_READ);
   if (rc == 0)