doc/APIchanges: fill in missing hashes and dates.

doc/APIchanges

@@ -13,21 +13,21 @@ libavutil:   2011-04-18
 
 API changes, most recent first:
 
-2011-05-10 - xxxxxxx - lavc 53.3.0 - avcodec.h
+2011-05-10 - 188dea1 - lavc 53.3.0 - avcodec.h
   Deprecate AVLPCType and the following fields in
   AVCodecContext: lpc_coeff_precision, prediction_order_method,
   min_partition_order, max_partition_order, lpc_type, lpc_passes.
   Corresponding FLAC encoder options should be used instead.
 
-2011-04-XX - bebe72f - lavu 51.1.0 - avutil.h
+2011-04-26 - bebe72f - lavu 51.1.0 - avutil.h
   Add AVPictureType enum and av_get_picture_type_char(), deprecate
   FF_*_TYPE defines and av_get_pict_type_char() defined in
   libavcodec/avcodec.h.
 
-2011-04-xx - 10d3940 - lavfi 2.3.0 - avfilter.h
+2011-04-26 - 10d3940 - lavfi 2.3.0 - avfilter.h
   Add pict_type and key_frame fields to AVFilterBufferRefVideo.
 
-2011-04-xx - 7a11c82 - lavfi 2.2.0 - vsrc_buffer
+2011-04-26 - 7a11c82 - lavfi 2.2.0 - vsrc_buffer
   Add sample_aspect_ratio fields to vsrc_buffer arguments
 
 2011-04-21 - 94f7451 - lavc 53.1.0 - avcodec.h