[librsvg] (14 commits) ...Merge branch 'update-gtk-rs'

[Federico Mena Quintero <federico src gnome org>]

Summary of changes:

  eb87658... c_api: function to convert bool gerrors
  3f9cbce... c_api: turn into_bool_gerror into a trait so we can do resu
  2be2335... Missed a few conversions
  ffaeb8b... Don't return an empty result in check_cairo_context
  e022199... c_api: check the cairo status by hand in preparation for th
  6eed1d3... Update gtk-rs dependencies
  28b0b28... initial port to gtk-rs 0.9
  94af19e... Convert the gflags to glib-rs's new macros
  ec1c0db... Convert RSVG_ERROR_FAILED to the new genum proc-macro
  898e6b7... Remove unnecessary mutable references, per clippy
  ce49ed8... DrawingCtx.set_color never fails; don't return Result
  3507762... DrawingCtx::set_gradient can't fail, so don't return a Resu
  e07c8a5... cargo fmt
  13cb3f5... Merge branch 'update-gtk-rs'