Drop the pure Perl implementations of the encoders and
decoders. They are bloat that hides real problems in
the XS implementations. I will re-release them separately
in the new MIME-Base64-Perl distribution.
The 'gcc -Wall' fix in 2.22 broke support for perl5.005,
as the isXDIGIT() macro is not available in that perl.
This problem has now been fixed.