Support rpmautospec

Add a new switch

variables:
  RPM_AUTOSPEC: 'True'

This will process all .spec files through rpmautospec to expand in particular %autochangelog and %autorelease

To migrate and existing RPM to use rpmautospec run:

rpmautospec convert myexample.spec

• https://docs.pagure.org/fedora-infra.rpmautospec/