Quiet warning in a DEBUG print

The variable type is STRLEN, and the format
code is expecting a UV, so just cast it to UV
to quiet a warning.
Fix typo in perlreapi(1perl).
Add Nathan Trapuzzano to AUTHORS
Suppress system Term::ReadLine::Gnu

perl5db.t will die in Term::ReadLine if Term::ReadLine::Gnu is installed
in the system. Let's favour core implementation.

Best solution would be to prune @INC to prevent from loading already
installed modules like this:

BEGIN {
    use Config;
    @INC = grep { ! /^\Q$Config{installprefix}\E(\/|\z)/ } @INC;
}

However that is not possible (now) due to various execs (even without
proper -I) in the harness chain. perl should implement -nostdinc
option.

Signed-off-by: Petr Písař <ppisar@redhat.com>
'Prototype after' and 'Illegal character' warnings should both pretty print the prototype text.

For example, prior to this patch,
eval "sub foo (@\0) {}"
would give two warnings:

Prototype after '@' for main::foo : @ at (eval 1) line 1.
Illegal character in prototype for main::foo : @\0 at (eval 1) line 1.

In both cases, the representation which makes a NULL visible
is useful, and of course since we're printing the same warning twice,
it doesn't hurt to display it consistently.