Sets a human-readable name for the application. This name should be
localized if possible, and is intended for display to the user.
Contrast with g_set_prgname(), which sets a non-localized name.
g_set_prgname() will be called automatically by gtk_init(),
g_set_application_name() will not.
Note that for thread safety reasons, this function can only be called once.
The application name will be used in contexts such as error messages, or when displaying an application’s name in the task list.