mpegaudio float decoders depend on dct

Originally committed as revision 23945 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -1195,6 +1195,11 @@ ljpeg_encoder_select="aandct"
 loco_decoder_select="golomb"
 mjpeg_encoder_select="aandct"
 mlp_decoder_select="mlp_parser"
+mp1float_decoder_select="dct"
+mp2float_decoder_select="dct"
+mp3adufloat_decoder_select="dct"
+mp3float_decoder_select="dct"
+mp3on4float_decoder_select="dct"
 mpeg1video_encoder_select="aandct"
 mpeg2video_encoder_select="aandct"
 mpeg4_decoder_select="h263_decoder mpeg4video_parser"