1.12-rc3 Unstable

This is another 1.12 release candidate fixing bugs and updating a lot of translations.

    * Fixes #459: Fixes GtkDoc warnings
      (Leiaz)
    * Fixes #415: Filter commands are not asynchronous
      (Rich Coe)
    * Fixes #363: Missing space above internal browser address bar
      (reported by nekohayo, patch by Mikel Olasagasti)
    * Fixes #208: All "Unread" search folder items marked read at once
      (Leiaz)
    * Fixes #251: Liferea does not always use theme icons when it is launched
      on system startup (reported by GreenLunar, fix by Leiaz)

    * Updated Finnish translation (Jorma Karvonen)
    * Updated Latvian translation (Rihards Prieditis)
    * Updated Albanian translation (Bensik Bleta)
    * Updated Hungarian translation (Balázs Úr)
    * Updated Brazlian translation (Rafael Ferreira)
    * Updated French translation (Guillaume Bernard)