Log Message:
Update to 1.4.23. From the changelog:

documentation:

* Improve documentation for OmegaScript numerical and logical operators.  Patch
  from Vaibhav Kansagara.

* Improve documentation for DATEVALUE, xFILTERS and $filters.

indexers:

* omindex:

  + Handle XPS files with multiple FixedDocument parts better.  Previously we
    only extracted text from the first FixedDocument part.

  + Prefer latter subparts of multipart/alternative which is what RFC2046 (and
    earlier RFCs which that obsoletes) say, but previously we used the first
    subpart that we could get text from.

  + Prefer latter subparts of multipart/alternative when indexing Outlook
    .msg files too.

  + Fix obscure bug in --mimetype option.  We keep track of the length of the
    longest extension we have a mapping for, but this was being updated using
    the length of the MIME type rather than the length of the extension.
    Theoretically this could have led to us effectively ignoring a --mimetype
    option, but in the real world the MIME type will probably always be longer
    so this just results in us testing long extensions unnecessarily.

omega:

* Ignore DATEVALUE CGI parameter if START.n, etc is specified on the same
  slot.  We explicitly document not to do this, but if that advice is ignored
  it's more helpful to at least preserve the property that we only have
  one date range per value slot.

* Add flag_ngrams as a preferred new alias for flag_cjk_ngram.  In the next
  release series this feature has been expanded to cover many more languages
  so the "cjk" in the name has become inaccurate as it stands for
  "Chinese, Japanese and Korean").

* Fix handling of Outlook .msg containing Unicode.  Codepoints <= U+00FF appear
  to have been handled correctly, but anything higher resulted in individual
  bytes of the UTF-8 encoding being treated as separate characters.

  Fixes https://github.com/xapian/xapian/pull/326, reported by uhuntu.

portability:

* Fix compatibility code for old libmagic versions.  The code we were using
  seems like it would never have worked.  Nobody's reported this (it was
  spotted while looking at the code) so we could just require libmagic >= 4.22,
  but it's trivial to actually handle so we've fixed the fallback code.

* Remove lingering traces of IRIX support as it's been dead for many years.