Fix annoying error message (Release 0.6.1).

checkmail prints an error message like
  Argument "AI_NUMERICHOST" isn't numeric in subroutine
  entry at /usr/lib/perl5/Net/DNS/Resolver/Base.pm
  line 743.
every time. Change shebang to "perl -w" from "perl -W".

Update version number (in comment line too, where it
was stillt 0.5).

Update TODO and Changelog.

Include TODO in repository.

Release 0.6.1 (maintenance).

Signed-off-by: Thomas Hochstein <thh@inter.net>