Friendlier flags for B

By default, "$foo->flags" when passed an object in the "B" class will
produce a relatively meaningless number, which one would need to grovel
through the Perl source code in order to do anything useful with. This
module adds "flagspv" to the SV and op classes and "privatepv" to the op
classes, which makes them easier to understand.

WWW: https://metacpan.org/release/B-Flags