Investigate whether input widgets with keypad navigation should avoid clearing their contents when losing and regaining edit focus

When you unfocus and refocus a line edit (for example by switching to home screen and back), the next typed character will erase everything, which is very annoying.

Here is how to reproduce:

1. Keypad navigation must be on.
2. Focus a lineedit and start typing.
3. Switch to a different window.
4. Switch back.
5. When you start typing again, everything is erased.

S60's motivation for changing this is the following use case:
A user types into a line or text edit, and gets interrupted by for example phone call or an SMS. This causes the active application to lose focus, which again causes edit focus to be lost. When resuming the application the focus gets set back, but the edit focus does not (nor should it). However, when the user types the next character, the line edit will erase all contents of the widget because it did not have edit focus. This is extremely destructive for a mobile phone user, especially since undo is not easily available.