Fix build of audio/kwave on -CURRENT (or with clang 9 in general).
There's a long description in the patch just added, but the error
looks something like this:
/tmp/v.cpp:1:27: note: constrained by private inheritance here
class foo {}; class bar : private foo {}; class baz : public bar { publi...
No PORTREVISION because it's no change for everyone except clang 9
users, who couldn't compile it previously.
Reported by: fallout