podcheck.t: Use scalar instead of array

The contents of @thankful_diagnostics are never used, only the length.
So it can simply be a scalar containing a count.
AUTHORS: Use tabs consistently

Since this is not just a source file, but a file to be read by the public
as is, we cannot mix tabs and spaces.
Carp: Stop polluting the caller's namespace if they lack @CARP_NOT or @ISA

Turns out that this:

perl -MCarp -le 'package Foo; eval { Carp::croak(1) }; print keys %Foo::;'

Would leave two new symbols in Foo, CARP_NOT and ISA. This commit
changes trusts_directly() to check if the symbols exists in the
stash before using them.
Carp: Don't autovivify the CARP_NOT or ISA array

In this situation:

    use Carp;
    package Foo;
    $CARP_NOT = 1;
    warn *{$Foo::{CARP_NOT}}{ARRAY} || 'undefined';
    eval { Carp::croak(1) };
    warn *{$Foo::{CARP_NOT}}{ARRAY} || 'undefined';

The second warn shows that Carp is autovivifying the ARRAY slot
of the glob.  This commit builds on the previous and checks that
the array exists before trying to use it.
Bump version in Carp::Heavy.
perldiag: Tweak ‘'%c' allowed only after types’

by adding ‘in %s’ to the end.  Though strictly unnecessary, having
more of the unvarying parts of the string displayed in perldiag is
generally a good thing, and this also appeases diag.t.  (The former is
my main reason for the change, the latter incidental.)