Use ARDOUR::ladspa_search_path and PBD::find_matching_files to find LADSPA modules
Add basic test for PluginManager and LADSPA plugins
Use g_stat in AudioSource::touch_peakfile for portability
Use g_utime for portability in AudioSource::touch_peakfile
Use g_rename in AudioSource::rename_peakfile for portability
Use g_stat in AudioSource::initialize_peakfile for portability