stdhandle.t: convert to use Test::More

print "ok 13\n" is *so* 1990's.
stdhandle.t: unlink the right file.

It writes to "afile", but initially deleted "afile.new" if it already
existed.
Tie::StdHandle appends extra copies of $\ to output

[perl #120202]

The following code demonstrates the problem:

    use Tie::Handle;

    my $out = do { no warnings 'once'; \ local *HANDLE };
    tie *$out, 'Tie::StdHandle', '>&', \ *STDOUT or die;

    $\ = "haha\n";
    print $out "hihi\n";

which prints

    hihi
    haha
    haha

The string in $\ has been added twice, once explicitly by
Tie::Handle::PRINT and another time implicitly by the use of
(CORE::) print in Tie::StdHandle::WRITE.

The bug also affects the use of say() with tied handles where a spurious
newline is added by the same effect.

[ test added by davem ]
Tie::StdHandle::WRITE: handle offset

the WRITE method was ignoring its offset argument.
bump Tie::StdHandle version

after recent fixes