Initial import. Needed by upcoming patches which port virtual_oss to
base.
Sponsored by: The FreeBSD Foundation
git-subtree-dir: contrib/libsamplerate
git-subtree-mainline: d2761422eb0a811976390743921b3f15e9d8331a
git-subtree-split: 69a539a327ef8d78260056c5394363569b5751ef