Copyright for rust-clang-sys source package in Focal

Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
Upstream-Name: clang-sys
Upstream-Contact: Kyle Mayes 
Source: https://github.com/KyleMayes/clang-sys

Files: *
Copyright: 2015-2018 Kyle Mayes 
License: Apache-2.0

Files: debian/*
Copyright:
 2018-2020 Debian Rust Maintainers 
 2018 Ximin Luo 
 2019-2020 Daniel Kahn Gillmor 
License: Apache-2.0

License: Apache-2.0
 Debian systems provide the Apache 2.0 license in
 /usr/share/common-licenses/Apache-2.0