Stream improvements.

* include/mailutils/stream.h (mu_stream_printf): Mark as printf-like.
* include/mailutils/sys/stream.h (_MU_STR_EVENT_CLOSE): New event.
(_mu_stream) <event_cb_data>: New member.
* libmailutils/stream.c (mu_stream_seek): Avoid unnecessary seeks
in mu_buffer_none mode.  Complements 906499db.
(mu_stream_close): Mark _MU_STR_EVENT_CLOSE event.

@@ -140,7 +140,8 @@ int mu_stream_set_flags (mu_stream_t stream, int fl);
 int mu_stream_clr_flags (mu_stream_t stream, int fl);
 
 int mu_stream_vprintf (mu_stream_t str, const char *fmt, va_list ap);
-int mu_stream_printf (mu_stream_t stream, const char *fmt, ...);
+int mu_stream_printf (mu_stream_t stream, const char *fmt, ...)
+                      MU_PRINTFLIKE(2,3);
 
 int mu_stream_copy (mu_stream_t dst, mu_stream_t src, mu_off_t size,
 		    mu_off_t *pcsz);

@@ -28,6 +28,7 @@
 #define _MU_STR_EVENT_CLRFLAG   1
 #define _MU_STR_EVENT_FILLBUF   2
 #define _MU_STR_EVENT_FLUSHBUF  3
+#define _MU_STR_EVENT_CLOSE     4
 
 #define _MU_STR_EVMASK(n) (1<<(n))
 
@@ -63,6 +64,7 @@ struct _mu_stream
 
   void (*event_cb) (struct _mu_stream *, int code, unsigned long, void *);
   int  event_mask;
+  void *event_cb_data;
   
   const char *(*error_string) (struct _mu_stream *, int);
   

@@ -375,10 +375,11 @@ mu_stream_seek (mu_stream_t stream, mu_off_t offset, int whence,
       return mu_stream_seterr (stream, EINVAL, 1);
     }
 
-  if ((stream->buftype == mu_buffer_none && offset != stream->offset)
-      || stream->level == 0
+  if (stream->buftype == mu_buffer_none ?
+      (offset != stream->offset)
+       : (stream->level == 0
 	  || offset < stream->offset
-      || offset > stream->offset + stream->level)
+	  || offset > stream->offset + stream->level))
     {
       if ((rc = _stream_flush_buffer (stream, 1)))
 	return rc;
@@ -945,10 +946,12 @@ mu_stream_close (mu_stream_t stream)
     
   if (!stream)
     return EINVAL;
+  
   mu_stream_flush (stream);
   /* Do close the stream only if it is not used by anyone else */
   if (stream->ref_count > 1)
     return 0;
+  _stream_event (stream, _MU_STR_EVENT_CLOSE, 0, NULL);
   if (stream->close)
     rc = stream->close (stream);
   return rc;