Audio rework, new jitter buffer

Jitter buffer is now based on packets, not on samples. The frames are
dejittered in received form. After reading from jitter buffer, they are
decoded in correct order. If a frame is missing, it is concealed by
repeating audio.

src/pocsag/pocsag.c

@@ -565,7 +565,7 @@ void call_down_release(int callref, int cause)
 }
 
 /* Receive audio from call instance. */
-void call_down_audio(int __attribute__((unused)) callref, uint16_t __attribute__((unused)) sequence, uint32_t __attribute__((unused)) timestamp, uint32_t __attribute__((unused)) ssrc, sample_t __attribute__((unused)) *samples, int __attribute__((unused)) count)
+void call_down_audio(void __attribute__((unused)) *decoder, void __attribute__((unused)) *decoder_priv, int __attribute__((unused)) callref, uint16_t __attribute__((unused)) sequence, uint8_t __attribute__((unused)) marker, uint32_t __attribute__((unused)) timestamp, uint32_t __attribute__((unused)) ssrc, uint8_t __attribute__((unused)) *payload, int __attribute__((unused)) payload_len)
 {
 }