Walk does not do a good job managing icons not obtained via resources

[dblohm7]

eg let's say I've got an HICON from something (maybe I created it myself via CreateIcon) and create a *walk.Icon from it. Walk doesn't handle dpi scaling etc like it does when they come from resources, nor does it really provide a way for us to do so when we created the walk.Icon.

This makes it harder to do any programmatic modifications to icons.