Log Message:
librsvg: update to 2.54.4

Version 2.54.4
==============

- #817 - Support CSS Color 4 syntax for `<alpha-value>`.  Opacities
  can be specified as numbers or percentages now, e.g. `0.5` or `50%`
  (Michael Howell).

- #870 - Roll back minimum required version of Pango to 1.46.0
  (Kleis Auke Wolthuizen).

- #867 - Fix Windows NMake install when documentation is not built.
  (Peter Williams).