Externals: update cubeb to kinetiknz/cubeb@c2bd582

A bunch of changes, looks mainly like bug fixes and code cleanup.

Notable changes:
- `cubeb_get_min_latency`'s signature was changed to take params via
  pointer, requiring Dolphin code to be tweaked in two places.
- A fix for kinetiknz/cubeb#320, as reported by @shuffle2
- Fixed build on FreeBSD (kinetiknz/cubeb#344), as contributed by @endrift

Externals/cubeb/Config.cmake.in

@@ -0,0 +1,4 @@
+@PACKAGE_INIT@
+
+include("${CMAKE_CURRENT_LIST_DIR}/cubebTargets.cmake")
+check_required_components(cubeb)