/usr/include/libbuzztard-core/ is in libbuzztard-dev 0.6.0-1.1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/libbuzztard-core/application.h
/usr/include/libbuzztard-core/childproxy.h
/usr/include/libbuzztard-core/core.h
/usr/include/libbuzztard-core/gconf-settings.h
/usr/include/libbuzztard-core/machine.h
/usr/include/libbuzztard-core/pattern.h
/usr/include/libbuzztard-core/persistence.h
/usr/include/libbuzztard-core/plainfile-settings.h
/usr/include/libbuzztard-core/processor-machine.h
/usr/include/libbuzztard-core/sequence.h
/usr/include/libbuzztard-core/settings.h
/usr/include/libbuzztard-core/setup.h
/usr/include/libbuzztard-core/sink-bin.h
/usr/include/libbuzztard-core/sink-machine.h
/usr/include/libbuzztard-core/song-info.h
/usr/include/libbuzztard-core/song-io-native-bzt.h
/usr/include/libbuzztard-core/song-io-native-xml.h
/usr/include/libbuzztard-core/song-io-native.h
/usr/include/libbuzztard-core/song-io.h
/usr/include/libbuzztard-core/song.h
/usr/include/libbuzztard-core/source-machine.h
/usr/include/libbuzztard-core/tools.h
/usr/include/libbuzztard-core/version.h
/usr/include/libbuzztard-core/wave.h
/usr/include/libbuzztard-core/wavelevel.h
/usr/include/libbuzztard-core/wavetable.h
/usr/include/libbuzztard-core/wire-pattern.h
/usr/include/libbuzztard-core/wire.h