add a missing word in perllexwarn
assume "all" in "use warnings 'FATAL';" and related

Until now, the behavior of the statements

 use warnings "FATAL";
 use warnings "NONFATAL";
 no warnings "FATAL";

was unspecified and inconsistent. This change causes them to be handled
with an implied "all" at the end of the import list.

Tony Cook: fix AUTHORS formatting
[perl #120977] bump $warnings::VERSION
[perl #120977] use warnings "FATAL" implies "all"