Documentation and changelog update for libspeex decoding

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@15698 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

Changelog

@@ -138,6 +138,7 @@ version <next>
 - Nellymoser ASAO encoder
 - ASS and SSA demuxer and muxer
 - liba52 wrapper removed
+- Speex decoding via libspeex
 
 version 0.4.9-pre1:
 

doc/general.texi

@@ -409,6 +409,8 @@ following image formats are supported:
     @tab experimental codec
 @item Sonic lossless         @tab  X  @tab  X
     @tab experimental codec
+@item Speex                  @tab     @tab  X
+    @tab Supported through the external libspeex library.
 @item THP ADPCM              @tab     @tab  X
     @tab Used on the Nintendo GameCube.
 @item True Audio (TTA)       @tab     @tab  X