Add /* AGENT_SHEET */ comment for Stylish 1.4.1
https://addons.mozilla.org/addon/stylish/versions/1.4.1
https://github.com/JasonBarnabe/stylish/wiki/Overwriting-page-styles#agent_sheet
Hide .toolbarbutton-multiline-text on Firefox 29+ and SeaMonkey 2.26+
Always show tab icon (for Australis)