This amends 5950df2b74. The VST3 SDK does not recursively search
directories that are bundles IFF the file inside the bundle's
architecture folder matches the bundle's name.
In case there's a file with a different name resides inside the
bundle it is treated as standalone, unbundled plugin.
Since Ardour, PBD::Searchpath always does a recursive search, the
bundled plugins need to be weeded after the fact.
This now follows the VST3 SDK by not just checking the arch name,
but also Contents and bundle.vst3 parent dirnames.
When using the export-tool, the very first callback may already be
freewheeling. In this case the first call to the butler also happens
directly from the freewheel process-callback and initial session events
are handled there. Setting PostTransportAdjustPlaybackBuffering
took the process-lock, which caused a deadlock:
Glib::Threads::Mutex::Lock::Lock(Glib::Threads::Mutex&) at /usr/include/glibmm-2.4/glibmm/threads.h:687
ARDOUR::Session::butler_transport_work() at ../libs/ardour/session_transport.cc:1157
ARDOUR::Session::process_export_fw(unsigned int) at ../libs/ardour/session_export.cc:303
ARDOUR::AudioEngine::process_callback(unsigned int) at ../libs/ardour/audioengine.cc:486
ARDOUR::DummyAudioBackend::main_process_thread() at ../libs/backends/dummy/dummy_audiobackend.cc:951
This fixes an issues with missing monitor-sends when creating
a session from a template with monitor-section, or when creating
tracks from a route-template.
When exporting long sessions with freewheeling, pulseaudio
may meanwhile suspend the corked audio device. The "FAIL_ON_SUSPEND"
option then prevents ardour to uncork it after export, and the
audio-backend is halted.
*PluginInfo::load() eventually calls `plugin->set_info()`
which depends on a valid PluginPtr. The method needs to return
early if `plugin` is unset or null.
