Adding license header for files to be ported form musl-libc

[Eshan Dhawan]

Hello everyone,
I plan to port ftw.h header and its methods from musl-libc library but the
header file does not have a license header, instead they have a combined
copyright file and it is too large to add to the header. Is it possible to
add the copyright file as musl.license or similar and reference it in the
header.
Copyright file from musl :
https://git.musl-libc.org/cgit/musl/tree/COPYRIGHT
<https://www.google.com/url?q=https://git.musl-libc.org/cgit/musl/tree/COPYRIGHT&sa=D&source=hangouts&ust=1592934259455000&usg=AFQjCNGD0yDy0Qv-CqIW1b18pi3jrB79JA>

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Thanks
- Eshan