updated libopus and Opus build scrips

libs/opus/include/opus/opus.h

@@ -616,7 +616,10 @@ OPUS_EXPORT void opus_pcm_soft_clip(float *pcm, int frame_size, int channels, fl
   * merged. Splitting valid Opus packets is always guaranteed to succeed,
   * whereas merging valid packets only succeeds if all frames have the same
   * mode, bandwidth, and frame size, and when the total duration of the merged
-  * packet is no more than 120 ms.
+  * packet is no more than 120 ms. The 120 ms limit comes from the
+  * specification and limits decoder memory requirements at a point where
+  * framing overhead becomes negligible.
+  *
   * The repacketizer currently only operates on elementary Opus
   * streams. It will not manipualte multistream packets successfully, except in
   * the degenerate case where they consist of data from a single stream.

libs/opus/include/opus/opus_defines.h

@@ -713,6 +713,10 @@ extern "C" {
 OPUS_EXPORT const char *opus_strerror(int error);
 
 /** Gets the libopus version string.
+  *
+  * Applications may look for the substring "-fixed" in the version string to
+  * determine whether they have a fixed-point or floating-point build at
+  * runtime.
   *
   * @returns Version string
   */