Fix and complete copyright notices in Makefile.am files.

Fix and complete copyright notices in Makefile.am files.

* Makefile.am: Use single-`#' comment for copyright notice, so
that it also appears in the generated Makefile.in file.
* doc/Makefile.am: Likewise.
* doc/amhello/Makefile.am: Likewise.
* doc/amhello/src/Makefile.am: Likewise.
* lib/Automake/Makefile.am: Likewise.
* lib/Automake/tests/Makefile.am: Likewise.
* lib/Makefile.am: Likewise.
* lib/am/Makefile.am: Likewise.
* m4/Makefile.am: Likewise.
* tests/Makefile.am: Add copyright notice.
Report of missing copyright notice by Stefano Lattarini.

Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>