Issues with QFileDialog static methods in Symbian^3

QFileDialog static methods utilize Native Symbian file dialog in Symbian^3. There are few issues with it that could be improved:

• The file path returned by methods has Symbian native backslashes instead of the expected slashes for directory separator.
• QFileDialog::getSaveFileName method can include a filename in dir parameter which will be used as default file name. This kind of functionality is supported by Symbian native file dialog also, but is not currently used.