Re: Announcement: libvdpau is moving to its own package
libvdpau_trace doesn't need any versioning because both libvdpau.so and libvdpau_trace.so are built together from the same source package, and libvdpau_trace.so is only used by libvdpau.so; it's never "publicly" exposed.
I suppose there's some merit to the argument that because libvdpau_trace.so is a private/internal library, it should be placed into a sub-directory of /usr/lib. This seems slightly like Debian imposing arbitrary packaging restrictions on upstream packages though. I'll look into other packages/distros, and whether configure can allow distros to configure the package to work the way they want...