Methods QString::fromAscii and QString::toAscii have been deprecated in Qt 5 (https://doc.qt.io/qt-5/qstring-obsolete.html).
This commit replaces calls to QString::fromAscii by calls to QString::fromLatin1 and calls to QString::toAscii by calls to QString::toLatin1.
This allows successful build when merging branch master into branch qt5.
Current VGM format implementation in GStreamer (gstgme) only supports Sega Geneses (Mega Drive) and Sega Master System emulation.
GStreamer also cannot handle the VGZ format (a shorthand for vgm.gz, a gzipped archive that contains a song) which means
that users will currently have to extract the contents of their VGZ files to individual vgm files.
