lossless mjpeg encoding (planar yuv & RGB) and somerelated bugfixes

Originally committed as revision 1968 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/allcodecs.c

@@ -63,6 +63,7 @@ void avcodec_register_all(void)
     register_avcodec(&wmv2_encoder);
 #endif
     register_avcodec(&mjpeg_encoder);
+    register_avcodec(&ljpeg_encoder);
     register_avcodec(&huffyuv_encoder);
     register_avcodec(&asv1_encoder);
     register_avcodec(&ffv1_encoder);