Change ARDOUR::init return type to bool type for success/failure
Prevent libardour from being initialized more than once

This is not thread safe of course, it is not intended to be.

This was implemented as at one stage ARDOUR::init was being called multiple
times in the testsuite which was causing a subtle bug that took some
time to track down.
Move initialization of libardour from ARDOUR_UI class into main()
Add PBD::init and PBD::cleanup

A bit of refactoring to move initialization of libpbd into libpbd
rather than rely on "client" code(ui,libardour,tests etc) to do it
Call PBD::init in ARDOUR::init and PBD::cleanup in ARDOUR::cleanup
Call Gio::init from PBD::init instead of ARDOUR::init

PBD needs Gio for PBD::copy_file and perhaps others
Call setup_libpbd_enums in PBD::init for portability
Remove call to PBD::ID::init as it is now done via ARDOUR::init
Move curve test file handling in main() until after ARDOUR::init is called

This means it doesn't need to call PBD::ID::init directly, which it now
shouldn't be doing
check master sources when determining whether a region uses a source. should fix #5618
fix newly-appearing crash-at-close caused by muddled thinking in pbd/pthread_utils

threads created with this code can now just return a value as they normally would, and the
infrastructure will ensure cleanup. there is no longer any reason to call pthread_exit_pbd()
and so that has been removed.
update czech translations from pavel fric
update czech translations from pavel fric, part 2
undo the hiding of SR-dependent LV2 ports
don't run meter in import-dialog if the dialog is not visible
export: add support for CAF
Merge branch 'master' into cvnc