[Qt] Pop debug window in foreground when opened twice

[maflcko]

Currently the debug window stays in the background when opened a second time. It should pop up in the foreground, instead.

The commit is pretty much a conceptual copy of 5ffaaba and 382e9e2.

[Diapolo]

Nit: Please remove one of the new-lines.

[Diapolo]

Seems to be another try like mine with #6288.

[jonasschnelli]

Tested ACK.
Binaries: https://builds.jonasschnelli.ch/pulls/6653/

[maflcko]

@Diapolo Thanks for the feedback. I have rearranged the commits according to comments. The rename commit is now HEAD, so it can be easily dropped.

@jonasschnelli Thanks for the binaries. The binaries are using now outdated a bit because I force pushed ed2c72e in the meantime. You can expect the following from ed2c72e:

Debug window ...	Mac OS [fanquake]	Fedora Linux (GNOME)	Windows 7
... on another virtual desktop:	switch to virtual desktop and show	switch to virtual desktop and show	n.a.
... hidden behind other windows:	raise to foreground	raise to foreground	raise to foreground
... minimized:	show	n.a.	show

[fanquake]

Tested ed2c72e on OS X

On another virtual desktop: switch to virtual desktop and show
Hidden behind other windows: raise to foreground
Minimised: show

[maflcko]

Trivial rebase (3-way merge)

[jonasschnelli]

ReACK.