doc/APIchanges: fill in missing dates and hashes.

doc/APIchanges

@@ -13,23 +13,23 @@ libavutil:     2011-04-18
 
 API changes, most recent first:
 
-2012-10-xx - xxxxxxx - lavr 1.0.0 - avresample.h
+2012-10-05 - e7ba5b1 - lavr 1.0.0 - avresample.h
   Data planes parameters to avresample_convert() and
   avresample_read() are now uint8_t** instead of void**.
   Libavresample is now stable.
 
-2012-09-23 - xxxxxxx - lavc 54.28.0 - avcodec.h
+2012-09-24 - a42aada - lavc 54.28.0 - avcodec.h
   Add avcodec_free_frame(). This function must now
   be used for freeing an AVFrame.
 
-2012-09-12 - xxxxxxx - lavu 51.41.0 - audioconvert.h
+2012-09-12 - 8919fee - lavu 51.41.0 - audioconvert.h
   Added AV_CH_LOW_FREQUENCY_2 channel mask value.
 
-2012-09-04 - xxxxxxx - lavu 51.40.0 - opt.h
+2012-09-04 - 686a329 - lavu 51.40.0 - opt.h
   Reordered the fields in default_val in AVOption, changed which
   default_val field is used for which AVOptionType.
 
-2012-xx-xx - xxxxxxx - lavc 54.26.1 - avcodec.h
+2012-08-30 - a231832 - lavc 54.26.1 - avcodec.h
   Add codec descriptor properties AV_CODEC_PROP_LOSSY and
   AV_CODEC_PROP_LOSSLESS.