QSettings: If the string ends with trailing whitespace then it should be preserved and not stripped off

QSettings: If the string ends with trailing whitespace then it should be preserved and not stripped off as this would keep it in line with how Windows handles this situation. When a string is written with a \t at the end then Windows writes it as a tab. Whereas Qt will cause this to be stripped off instead.

Granted this would be a big change for Qt 4.8, but should be considered for Qt 5.0.