Make the Qt GUI backwards compatible with PyQt 4.7.3 (Qt 4.6.3). The
placeholderText property of QLineEdit class was introduced in Qt 4.7.
Fix Qt GUI bug where the context menu of the system tray icon is not displayed
Use a buffer instead of memoryview for backwards compatibility
Make version checks simpler and backwards compatible
Finish fixing SQLite NUL character 'bug'. Change type of received column in
inbox table from TEXT to INT.
Make timestamp comparisons regarding sound notification backwards compatible