be-gssapi-common.h should be located in src/include/libpq/

Hi all,

As mentioned on another thread about test coverage, I have noticed
that be-gssapi-common.h is not placed at the correct location, even
its its identication path at the top points to where the file should
be:
https://www.postgresql.org/message-id/20190604014630.GH1529@paquier.xyz

The file has been introduced at its current location as of b0b39f72.
Any objections to something like the attached?

Thanks,
--
Michael