Inset-icons are auto-scaled according to their width.
This is problematic, if converted from SVG
with the bounding box set to content (ignoring the page size)
and the content is not square.
OTOH, ignoring page size is done for good reasons - we usually want just
the drawing area when inserting an image into a document.
An invisible square with fixes this problem.
Some icons had spurious invisible elements outside the page -- leading
to too small results in the PDF. These were removed.
These icons are for lfuns that are not very interesting for users, but quite
often used when working on the LyX documentation. Now we can create a special
LyX documentation toolbar.
