Fix small titlebars option in GTK 3.20
Fix small titlebars option in GTK 3.20

gnunn1/tilix,gnunn1/tilix,Smando87/terminix,phw/terminix,phw/terminix,gnunn1/terminix,gnunn1/terminix,dsboger/tilix,gnunn1/tilix,dsboger/tilix,Smando87/terminix