poppler: enable splash backend by default

The splash backend is enabled by default, but it was made into an
explicit option in 42b31c4981c6c02749217dc9b7181a9f260dc823. This
resulted in it being *disabled* unless the option was passed, which
broke (at least) pdf2htmlex, which expects this functionality to be
present.

Fixes #26373.
gettext: add bottles
Updated sip with Python 3 compatibility
Refined code
Changed code to use more idiomatic Ruby. Added regex to determine Python version
Tweaked to match style guide
sip, pyqt: updated to match style guide, moved pythons hash into separate method