Some gtk icons are missing

[chmodsayshello]

Currently, there are a lot of gtk-specific icons missing, which leads to gtk based applications using fallback ones. In most cases, this could be resolved by making a copy of already existent files with the gtk name (which is how it's done for the gtk icons within this repository, "gtk-stop.png" is a link to "process-stop.png" etc.).

To see all gtk icons within a singular program, run gtk3-icon-browser (requires the package gtk-3-examples)

Examples of this issue:

(note that the preferences button has the correct icon due to gtk-preferences.png being there.)