wireshark: fix missing icon in taskbar
leafpad: make icon visible in taskbar/window decoration

on recent gtks it tries to use a codepath that only works
when "schemes" are installed and properly configured.
probably gtk-update-icon-cache or something similar.

instead we just do it the way it works everywhere.
add fake hicolor icon theme to fix icon errors

you can "butch rebuild hicolor-icon-theme-fake" whenever you
installed some new GTK app that doesnt display its icons correctly.
that will rebuild the gtk icon cache.
lxde: install fake hicolor icon theme