Fixed invalid report of broken avi index.

AVI demuxer now also check the number of frames from the index and the
avi header.

Thanks MSJ for the report on the forum.

modules/demux/avi/avi.c

@@ -673,7 +673,18 @@ aviindex:
 
     /* *** movie length in sec *** */
     p_sys->i_length = AVI_MovieGetLength( p_demux );
-    if( p_sys->i_length < (mtime_t)p_avih->i_totalframes *
+
+    /* Check the index completeness */
+    unsigned int i_idx_totalframes = 0;
+    for( unsigned int i = 0; i < p_sys->i_track; i++ )
+    {
+        const avi_track_t *tk = p_sys->track[i];
+        if( tk->i_cat == VIDEO_ES && tk->p_index )
+            i_idx_totalframes = __MAX(i_idx_totalframes, tk->i_idxnb);
+            continue;
+    }
+    if( i_idx_totalframes != p_avih->i_totalframes &&
+        p_sys->i_length < (mtime_t)p_avih->i_totalframes *
                           (mtime_t)p_avih->i_microsecperframe /
                           (mtime_t)1000000 )
     {