Add -ldl to libfaadbin_extralibs instead of libfaadbin_decoder_extralibs.

The latter does not exist and thus compilation fails.
patch by Janne Grunau, janne-ffmpeg jannau.net

Originally committed as revision 23087 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -1334,7 +1334,7 @@ libdirac_decoder_deps="libdirac !libschroedinger"
 libdirac_encoder_deps="libdirac"
 libfaac_encoder_deps="libfaac"
 libfaad_decoder_deps="libfaad"
-libfaadbin_decoder_extralibs='$ldl'
+libfaadbin_extralibs='$ldl'
 libgsm_decoder_deps="libgsm"
 libgsm_encoder_deps="libgsm"
 libgsm_ms_decoder_deps="libgsm"