Correct fullscreen multi monitor display on windows

If the primary monitor in a multi monitor setup on windows was not the top left most monitor in the monitor layout the render area would not extend to monitors above and to the left of the primary monitor. This patch corrects for this situation.
applied OF code style guides

spaces to tabs and camelcase var names.
Merge pull request #2927 from igierard/windows-multi-mon-fullscreen

Correct fullscreen multi monitor display on windows