DAVEM TPF Grant#3 December 2025 report

During December, I fixed assorted bugs, and started work on another
tranche of ExtUtils::ParseXS fixups, this time focussing on:

- adding and rewording warning and error messages, and adding new tests
  for  them;

- improving test coverage: all XS keywords have tests now;

- reorganising the test infrastructure: deleting obsolete test files,
  renaming the t/*.t files to a more consistent format; splitting a large
  test file; modernising tests;

- refactoring and improving the length(str) pseudo-parameter
  implementation.

By the end of this report period, that work was about half finished; it is
currently finished and being reviewed.

SUMMARY:
     10:25 GH #16197 re eval stack unwinding
      1:39 GH #23903 BBC: bleadperl breaks ETHER/Package-Stash-XS-0.30.tar.gz
      0:09 GH #23986 Perl_rpp_popfree_to(SV **sp) questionable design
      3:02 fix Pod::Html stderr noise
     27:47 improve Extutils::ParseXS
      1:47 modernise perlxs.pod
    ------
     44:49 TOTAL (HH::MM)