libmp3lame: don't check unused function in detection

hip_decode_init() isn't used by the wrapper, and can be absent from the
library if lame was configured with --disable-decoder (like it is done
for windows builds of VLC)

Unfortunately this also removes the way to detect a libmp3lame more recent
than the buggy 3.98.2

Patch by Rafaël Carré, rafael carre at gmail

Originally committed as revision 25391 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -2744,7 +2744,7 @@ enabled libdirac   && add_cflags $(pkg-config --cflags dirac) &&
                       require  libdirac libdirac_encoder/dirac_encoder.h dirac_encoder_init $(pkg-config --libs dirac)
 enabled libfaac    && require2 libfaac "stdint.h faac.h" faacEncGetVersion -lfaac
 enabled libgsm     && require  libgsm gsm/gsm.h gsm_create -lgsm
-enabled libmp3lame && require  "libmp3lame >= 3.98.3" lame/lame.h hip_decode_init -lmp3lame
+enabled libmp3lame && require  "libmp3lame >= 3.98.3" lame/lame.h lame_set_VBR_quality -lmp3lame
 enabled libnut     && require  libnut libnut.h nut_demuxer_init -lnut
 enabled libopencore_amrnb  && require libopencore_amrnb opencore-amrnb/interf_dec.h Decoder_Interface_init -lopencore-amrnb
 enabled libopencore_amrwb  && require libopencore_amrwb opencore-amrwb/dec_if.h D_IF_init -lopencore-amrwb