Relicense Win8 pointer input code as BSD 2-Clause

It's agreed on the mailing list that the Win8 pointer input support code
would be relicensed as BSD 2-Clause to allow usage by OpenToonz and
other projects.

In the future, other Krita developers who make changes to these two
files within Krita should agree to license their changes as BSD
2-Clause.

CC: kimageshop@kde.org