Add HELP_LINGUAS to the help Makefile
Fix conversion specifier in debug string
Remove a problematic debug string
Add Opus and Speex MIME types to desktop file
Revert "Refactor Scan_Convert_P20_Into_Space()"

This reverts commit 553ba87d0311e4e4c64f2321b5aa654df0c4ae29.

The above commit added a call to strcpy(), with arguments that
overlapped. The behaviour of such a call is undefined, and can lead to
test failures.

https://bugzilla.gnome.org/show_bug.cgi?id=728743
Move main window to EtApplicationWindow object
Pass the main window to actions as user data
Move log area to EtLogArea object
Move playlist window to EtPlaylistDialog object
Move load filenames dialog to EtLoadFilesDialog
Move file search dialog to EtSearchDialog object
Move preferences dialog to EtPreferencesDialog
Move CDDB dialog to EtCDDBDialog object
Move scan dialog to EtScanDialog object
Replace strncat() with g_string_append()
Move select and unselect actions to main window
Move file selection actions to EtApplicationWindow
Set a rough initial window size and pane positions
Move browser to EtBrowser object
Avoid a GtkApplication assertion

Realizaing an application window during construction triggers an
assertion with older versions of GTK+, and a warning with newer ones, so
only show the window after it has been associated with the application.