s/use base/use parent/

parent.pm does the same as base.pm, but [without the cruft](http://perldoc.perl.org/parent.html#HISTORY).

This patch serie:
- do not uses either base.pm or parent.pm where possible: it remove all instances of `use base qw(Exporter)` because inheriting from Exporter is not necessary since Exporter 5.57 (released with perl 5.8.3). Instead, only its `import` method is imported.
- uses parent.pm instead of base.pm in remaining places
- removes a useless inheritance on Exporter in autodie::hints