* [portmidi] Search for Threads in the CMake config.
Without this, consuming the library in CMake would result in the
following error:
The link interface of target "PortMidi::portmidi" contains:
Threads::Threads
but the target was not found.
* [portmidi] Cleanup portfile.
- Copy pdbs
- Use vcpkg_install_copyright
- Use ${VERSION}
* [portmidi] Install a usage file.
* [portmidi] Bump port-version.
* [portmidi] Update baseline.
