Upstream: https://github.com/xiph/opusfile.git
Version:  0.12-59-g6dfd29e (commit 6dfd29e7adb87f2e193575fc3fa88cbf1a0b27df)

Vendored by vendor.py in the parent directory; rerun it to update. It copies
the .c files the unity translation units compile and every header reachable
from them, and rewrites their includes as paths relative to the including
file.
