Install both cmake config and .pc file with CMake build

[barracuda156]

Currently CMake build only installs cmake config, while makefile build only installs .pc file. In result if libbinio is built with makefile, it cannot be used with CMake build of adplug (it fails to handle .pc file), while otherwise anything not using CMake won’t be able to find libbinio.

[barracuda156]

CMake also installs headers in a different location by default – directly into ${prefix}/include, while makefile build installs into ${prefix}/include/libbinio.