v1.004001

release v1.004001

 - document when is_bool became available
 - now favouring Cpanel::JSON::XS over JSON::XS in more situations (the former
   is always added to prereqs when a compiler is available, although JSON::XS
   is still used at runtime if new enough and Cpanel::JSON::XS is not
   installed). This makes boolean handling more predictable and consistent.