Log Message:
Update to 1.020

Upstream changes:
1.020  2024-03-04

- restructure _extract_inc(): always add XS DLLs in
  PAR_TEMP/inc to PAR::Heavy::FullCache, ie. even if PAR_TEMP/inc
  already exists (hence we don't need to extract the zip), cf. #11

- bump minimum perl version to 5.8.9 everywhere