ChangeLog:

  - Fix a11y labelling of several switches in the settings dialog
  - Fix an input window clipping bug in the tweet info page
  - Fix a few cases of overlapping widgets into window borders
  - Remove the "Save as" context menu from inline media. This ha
    not been working in a while but the context menu was still there.
  - Rename the .sidebar style class to .topbar. This was used in corebird
    before gtk+ used it, but now that the sidebar is at the top, the .sidebar
    style from gtk+ themes collides with the horizontal alignment we use,
    so use the more fitting '.topbar'.
  - Show a focus outline in the topbar again. We are setting a custom
    background color here, so we also need to set a fitting outline color.
  - Fix a coloring but in the topbar, where wildcard selectors in themes
    would overrde our foreground color.