Re #1219: protect new ffmpeg features with #ifdefs

git-svn-id: https://svn.pjsip.org/repos/pjproject/branches/projects/2.0-dev@3496 74dad513-b988-da41-8d7b-12977e46ad98
diff --git a/pjmedia/src/pjmedia-codec/ffmpeg_codecs.c b/pjmedia/src/pjmedia-codec/ffmpeg_codecs.c
index 78d8131..d9043d2 100644
--- a/pjmedia/src/pjmedia-codec/ffmpeg_codecs.c
+++ b/pjmedia/src/pjmedia-codec/ffmpeg_codecs.c
@@ -922,7 +922,9 @@
 	/* Set no delay, note that this may cause some codec functionals
 	 * not working (e.g: rate control).
 	 */
+#if LIBAVCODEC_VERSION_MAJOR >= 52 && LIBAVCODEC_VERSION_MINOR >= 113
 	ctx->rc_lookahead = 0;
+#endif
 
 	/* Open ffmpeg codec */
         pj_mutex_lock(ff_mutex);