Fully disable "raise on click" when unchecked

Fixes #232, see in particular #232 (comment 13711).

I feel like this is enough to get the expected behavior: no window comes to the foreground when clicking inside.

If ever a window has no edge, then it's still possible to raise it via the taskbar or alt-click if it appears in these lists, or using a "key+mouse button" combination configured in the accessibility settings.

Note that:

• CSD windows have edges (e.g. evince), or at least their menu bar acts as an edge that can be used to raise the window (so maybe #222 (closed) could be closed)
• "Child windows" without menu bar, like those thunar opens when trying to delete a file (without sending it to trash), also have some kind of edge (at the top)

So finally, I don't have an example of a truly borderless window, but again, if this ever had to exist, that wouldn't be a problem from my point of view.

EDIT: In fact, I have such an example: firefox or thunderbird with disabled title bar.
I wasn't using this setting until now because it broke the "don't raise on click" feature, but with the current patch it's ok.