help: make sure help shows with nice formatting
Starting with Perl 5.28.0, the default output when using
Pod::Usage with a verbose level >= 2 has been made plain,
ugly, no formatting whatsoever.
Compensate for this documentation travesty by setting
the PERLDOC environment variable, if it's not already set,
to restore the previous behavior.
Additionally, add the necessary changes so that the brief
help shown for '-h' will use terminal formatting codes to
show bold, underline, etc., if available, to avoid the very
ugly plain text mess that would otherwise appear.
Signed-off-by: Kyle J. McKay <mackyle@gmail.com>