Fix decode2047 test.

* mailbox/filter_iconv.c (mu_filter_iconv_create): Set filter flags.
* mailbox/fltstream.c (mu_filter_stream_create): Likewise.
* mailbox/qpflt.c (_qp_decoder): Handle '_'.

@@ -463,6 +463,7 @@ mu_filter_iconv_create (mu_stream_t *s, mu_stream_t transport,
   iptr->stream.ctl = _icvt_ioctl;
   iptr->stream.wait = _icvt_wait;
   iptr->stream.seek = _icvt_seek;
+  iptr->stream.flags = MU_STREAM_READ | MU_STREAM_SEEK;
   *s = (mu_stream_t)iptr;
   return 0;
 }

@@ -425,6 +425,7 @@ mu_filter_stream_create (mu_stream_t *pflt,
     fs->stream.seek = filter_seek;
   fs->stream.ctl = filter_ctl;
   fs->stream.error_string = filter_error_string;
+  fs->stream.flags = flags;
   
   fs->transport = str;
   fs->xcode = xcode;

@@ -142,6 +142,12 @@ _qp_decoder (void *xd MU_ARG_UNUSED,
 		  consumed += 2;
 		}
 	    }
+	  else if (c == '_')
+	    {
+	      *optr++ = ' ';
+	      nbytes++;
+	      consumed++;
+	    }
 	  else
 	    {
 	      *optr++ = c;