Better place to disable some mpeg4 code and ensure that

ff_write_quant_matrix() won't be used when mpeg4 encoder is disabled.

Originally committed as revision 9579 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/h263.c

@@ -2347,6 +2347,8 @@ static void mpeg4_encode_vol_header(MpegEncContext * s, int vo_number, int vol_n
 {
     int vo_ver_id;
 
+    if (!ENABLE_MPEG4_ENCODER)  return;
+
     if(s->max_b_frames || s->quarter_sample){
         vo_ver_id= 5;
         s->vo_type= ADV_SIMPLE_VO_TYPE;
@@ -2448,8 +2450,6 @@ void mpeg4_encode_picture_header(MpegEncContext * s, int picture_number)
     int time_incr;
     int time_div, time_mod;
 
-    if (!ENABLE_MPEG4_ENCODER)  return;
-
     if(s->pict_type==I_TYPE){
         if(!(s->flags&CODEC_FLAG_GLOBAL_HEADER)){
             if(s->strict_std_compliance < FF_COMPLIANCE_VERY_STRICT) //HACK, the reference sw is buggy