Fix lingering toolbox flickering
Radio button: fix behavior for "click when already true"

Copy/paste from the check box got me into trouble here.  :/

Ideally, I'd like to merge the check box and radio buttons into a single
control, with a "style" parameter that distinguishes the two.  That
would cut down on a lot of redundant code.

Unfortunately, it would also require a great deal of manual labor to
manually replace all instances of the unused control - so perhaps in
6.6.
showPDDialog: limit custom topmost dialog implementation to floating toolbox mode

This was a holdover from the old window manager implementation, when
image windows could also float.  VB's intrinsic .Show method works just
fine in non-floating mode, so no need to jump through extra window order
hoops.