build: stop tracking autotools products
build: drop rpm target
doc: update license headers

Update license headers to say "GPLv2 or later" instead of GPLv2 only.

Drop (C) date ranges from license header, retaining oldest date.
Copyright is then + 70 years, and this tempts gratuitous updating.

Drop list of original LMTv2 authors from licenese header, which were
there in an abundance of politeness, and retain only the module author.

Drop license headers from .h files as this is sometimes results in
a ridiculous signal/noise content and is probably unnecessary anyway
for non-installed headers.

Sort the AUTHORS file, ensure orig. LMTv2 authors are in there,
and add some recent contributors.
Prep for 3.1.8 release