Update to glibc copyright assignment policy

[Siddhesh Poyarekar]

On 7/29/21 1:20 AM, Carlos O'Donell via Libc-alpha wrote:
> branches. Code shared with other GNU packages via Gnulib will continue
> to require assignment to the FSF.

Does that mean we cannot touch the code shared with gnulib if we do not 
assign copyright to the FSF?  Or does it mean that if/when that happens, 
we will stop syncing those bits with gnulib?

Siddhesh