opusfile: Update to 0.12

Changes since the v0.11 release:

* Fix stack overflow buffering out-of-sequence streams.
* Fix possible divide-by-zero.
* Fix issues with seeking in the win32 backend.
* Fix an issue where the seek algorithm could be confused by stream data
  changing between reads.
* Clean up compiler and scan-build warnings.
* Avoid use of the deprecated ftime() function which has Y2038 problems.
* Remove undefined behaviour memcpy(NULL) in op_read_native().
* Visual Studio project files updated for libogg 1.3.4 library name
  change.
* Various build systems updates.
* Various integration and testing environment improvements.

This release is backward-compatible with the previous release. We
recommend all users upgrade.

(nia)