[pcre/f21] (3 commits) ...Fix compiler crash for zero-repeated groups with a recursive back reference

[Petr Pisar]

Summary of changes:

  5d1fed8... Fix empty-matching possessive zero-repeat groups in interpr (*)
  2e292a7... Fix memory leaks in pcregrep (*)
  01cdfc2... Fix compiler crash for zero-repeated groups with a recursiv (*)

(*) This commit already existed in another branch; no separate mail sent