Attempt to restore 5.12 compatibility

I've added mg_findext to perl 5.14.
Use %lu to format size_t arguments where perl doesn't support %zd
Merge branch 'rafl/5.12compat'

* rafl/5.12compat:
  Use %lu to format size_t arguments where perl doesn't support %zd
  Attempt to restore 5.12 compatibility