Input Unicode characters using Alt-+ on Windows

Normally on Windows it is possible to enter Unicode characters using Alt-+
and then hold alt while typing the hex code.

E.g.
alt-+ alt-3 alt-9 alt-b
should produce a Russian character.

This works fine in Notepad, but in Qt only using the number pad accepts
such kinds of input and it only accepts decimal input. Instead of showing the right
character Qt also prints the 'b' itself.

See http://www.windowsvistasecret.net/secret.asp?haber=54 for more information.