Surround AMR_WB encoding code by appropriate #ifdefs.

This will help support the opencore AMR library.

Originally committed as revision 18847 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/libamr.c

@@ -309,6 +309,8 @@ typedef struct AMRWBContext {
     Word16 allow_dtx;
 } AMRWBContext;
 
+#if CONFIG_LIBAMR_WB_ENCODER
+
 #include <amrwb/enc_if.h>
 
 static int getWBBitrateMode(int bitrate)
@@ -409,6 +411,8 @@ AVCodec libamr_wb_encoder =
     .long_name = NULL_IF_CONFIG_SMALL("libamr-wb Adaptive Multi-Rate (AMR) Wide-Band"),
 };
 
+#endif
+
 static av_cold int amr_wb_decode_init(AVCodecContext * avctx)
 {
     AMRWBContext *s = avctx->priv_data;