highgui CMakeLists.txt: ocv_list_unique makes for incorrect linking (Bug #2324)

In the highgui module's CMakeLists.txt, there is a command which filters the list of libraries for linking so that it is a unique list. The problem with this is that CMake library link lists can look something like this:

debug C:/dev/libs/QtCored4.lib optimized C:/dev/libs/QtCore4.lib
debug C:/dev/libs/QtGuid4.lib optimized C:/dev/libs/QtGui4.lib

The order of these options is essential, and after running through ocv_list_unique, all the duplicate entries of "debug" and "optimized" are removed, resulting in linking some release libraries in debug builds and debug libraries in release builds, depending on how the list was sorted and which library the linker encounters first (or last?).

I have attached a patch which fixes the issue but it needs to be reviewed. I don't know why that ocv_list_unique was there in the first place, but my fix is simply to remove it. Maybe that is enough and it works for me.