Version 2.43.0
- This is the start of the 2.43 development series, and you bet we are
  doing extensive changes!
- Many, many thanks to Jordan Petridis for keeping our Continuous
  Infrastructure updated all the time, and for emergency fixes when
  they were necessary.
- As part of the Summer of Code 2018, Ivan Molodetskikh is porting the
  filter effects to Rust.  These are done so far:  core filters
  infrastructure, feComposite, feMerge, feOffset.  The only remaining
  SVG elements done in C pertain to filter effects, and Ivan is taking
  care of them.
- The feComposite filter now operates in linear RGB space, for better
  spec compliance.  We transform back to SRGB for the final results
  (see issue #275 for pending work on fully supporting this
  elsewhere).
- Filters now compute their bounds to floating-point values, instead
  of clipping them to integers.
- The text, tspan, tref elements are now in Rust (Paolo Borelli).
- Text rendering should be better.  We now perform text measurement
  operations with the actual affine transformation that the text will
  use in the end.  This should give Pango/Freetype a better chance of
  doing scale-appropriate hinting.
- The basic styling infrastructure has moved to Rust (Paolo Borelli,
  Federico Mena).  We don't use the old and limited cascading code
  anymore.  We also audited which CSS properties are supposed to
  inherit automatically or not; this should be working per the SVG
  spec now.  Special thanks to Paolo for doing the largest part of the
  work in moving the style data to Rust; this was a painstaking,
  months-long process of constant refactoring.
- The internals of the drawing infrastructure and bounding-box
  computation are now done in Rust (Paolo Borelli).
- Element creation from the parsing stage is now in Rust (Saurav
  Sachidanand).
- Clipping and Masking are now done in Rust (Paolo Borelli).
- Our tests now include the full Adwaita icon theme, so it doesn't
  break.
- Fix: #241 - feDistantLight and feSpotLight now work again.
- Fix: #282 - feComposite is fixed not to overwrite the source image
  in some cases; this fixes drop shadows generated from Inkscape (Ivan
  Molodetskikh).
- We have the beginnings of Windows CI, courtesy of Guillaume Gomez.
- Changes from 2.42.4: