[no-copyright] Modified headers to reduce GPL license notice width
Copyright script will now ignore [no-copyright]-tagged commits (subject line)
Added additional generated files to linkchk ignores
Adjusted linkchk script to ignore now non-existant LICENSE and to check updated automake/autoconf files
linechk script now checking against 76 lines

The rationale is to give room for three characters for line numbering, plus
one delimiting space, for a total of an 80-characer-wide terminal.