[Win32] Properly show window on initialize (Foreground, Focus)

[f1nalspace]

The current way how I init a window before the message queue starts is not quite sufficient.
Sometimes the window won't show up, because it starts behind other windows.

I found that the combination of:

ShowWindow()
SetForegroundWindow()
SetFocus()

works much better.

[f1nalspace]

Implemented in develop branch