missing copyright line in clang headers

I was looking into reusing the clang cpuid.h header in
OpenBSD and the issue of a missing copyright line of the
form 'Copyright (c) YYYY Firstname Lastname" came up.

While the .cpp files all seem to have

// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.

The headers do not but instead have what looks like a license
text without the line. Given llvm/clang does not require
copyright assignment, http://llvm.org/docs/DeveloperPolicy.html#copyright
"As the copyright isn't held by the University of Illinois.

The LLVM project does not require copyright assignments, which means
that the copyright for the code in the project is held by its respective
contributors who have each agreed to release their contributed code
under the terms of the LLVM License."

It isn't clear who the copyright holder is for files in clang/lib/Headers.
Could someone clarify the intent here?