... after auto-removing some kinds of files by default.
In some cases I let them be removed and in others I let them be put into
$docdev. That was more due to general indecisiveness on this question
than any reasons in the particular cases.
- The split was only done where it seemed that some parts aren't really
needed, which were mainly headers and gtk-doc.
- Update style to be closer with what's common in nixpkgs.
- Change explicit removal of icon theme cache into including the
hicolor theme.
