Improving error message from neteq_rtpplay

If a packet with unknown RTP payload type is inserted, this CL
will make sure that the error message is a little more detailed
and gives a better understadning of what to do.

BUG=2692
R=tina.legrand@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/27909004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7603 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/modules/audio_coding/neteq/neteq_impl.h b/webrtc/modules/audio_coding/neteq/neteq_impl.h
index fc2284d..348f483 100644
--- a/webrtc/modules/audio_coding/neteq/neteq_impl.h
+++ b/webrtc/modules/audio_coding/neteq/neteq_impl.h
@@ -178,7 +178,7 @@
 
   // Returns the error code for the last occurred error. If no error has
   // occurred, 0 is returned.
-  virtual int LastError() OVERRIDE;
+  virtual int LastError() const OVERRIDE;
 
   // Returns the error code last returned by a decoder (audio or comfort noise).
   // When LastError() returns kDecoderErrorCode or kComfortNoiseErrorCode, check