AutoPrereq + "use feature 'foo'" adds feature.pm as a dependency [rt.cpan.org #78151]

[rjbs]

https://rt.cpan.org/Ticket/Display.html?id=78151

I ran into this bug by using AutoPrereq and "use feature 'say'", which
then added feature.pm as a dependency. I didn't notice until 100
CPANtesters failure reports said they couldn't find the feature.pm module.

This was discussed on #distzilla:

rjbs: If Perl::Prereqscanner sees "use feature 'current_sub'" it should
be adding perl 5.16.0 to the prereqs

Another similar case is that if you have "use foo 0.01", perl 5.12
should be added as a dep, since requiring a specific version of a Perl
module was added in 5.12.

The information in Module::CoreList should be sufficient to implement
this "missing feature"