Compile under Qt5.4. Please review the use of toUtf8 instead of toAscii

As we can install Qt 4 and 5 side by side and almost every distribution have the newer, even Debian Wheezy trough backports, I started to port Belle. With this minimal changes I can compile in 5.4.
But I'm not sure if `toAscii` can be changed to `toUtf8` without side effects to other part of code or if it should be `toLatin1`.
Nice. Then I will try to replace the class today.