nicely handle the (should-never-happen) case of no audio/MIDI backends being detected
add API to AudioBackend to allow discovery of possible MIDI I/O options
add JACK backend support for MIDI option discovery
basic use of new backend MIDI options
fix up parsing of send gain MIDI bindings so that they actually work
add API to get current MIDI option from an audio/MIDI backend
add API to get current MIDI option from an audio/MIDI backend
more fixes and rationalizations for MIDI option handling in the audio MIDI setup
some slightly hackish changes to make it possible to use the new internal ALSA midi client (soon to become a driver, however)
minor tweaks to audio/MIDI setup window
Fix script used to run libardour tests
Add get_test_sample_rate to common test functions in libardour tests
Delete test_globals.h/cc now that the contents has moved to test_common.h/cc
Update test to use correct SourceFactory::createWritable API
Use test_search_path to find test data files for automation test
return bool in test util function to check writing xml to file is successful
Add arg to test function to be able to prefix test output directory

This makes it much easier to find test output from a specific test
Write state data from automation list test to check why test is failing
Use test-env.sh in run-session-tests.sh

Also make the script executable
Add AudioEngine::set_default_backend