Fixing Qt Warning: Unescaped backslashes are deprecated!

From: http://www.openguru.com/2011/10/fixing-qt-warning-unescaped-backslashes.html

You might have hit this warning while you are trying to include source files located under sub directories to a Qt project.
Fix to solve this warning is very simple!
This warning occurs whenever you try to use backslash (\) as path separator. To avoid this warning just use forward slash (/) as your path separator, instead of backslash (\). Qt uses Unix style path separator (/) irrespective of the platform.
Example: If you want to include parent directory use ../ instead of ..\