To use this feature, derive your AudioProcessor from
VST3ClientExtensions and override getPluginHasMainInput() to return
false. The main input bus will then be designated as an Aux bus, rather
than a Main bus.

This is mainly useful for synth plugins like vocoders, which may need a
sidechain audio input, but which should replace all audio on the channel
with the output of the synth, rather than mixing with the audio input.

The AAX SDK already checks for truncated IDs internally. If any ID is
truncated, details will be written to Pro Tools' log file (you may need
to enable logging first). Search for "AAX_ASSERT" in the log to find
triggered assertions.

This behaves a lot like jassert, but will never emit unused-variable
warnings.

See commit message of a1337a38 for more details

- Add AlertWindow::show() and showAsync() methods that take a MessageBoxOptions argument
  - Add NativeMessageBox::show() and showAsync() methods that take a MessageBoxOptions argument
  - Update the DialogsDemo to demonstrate the new methods
  - Deprecate AlertWindow::showNativeDialogBox() in favour of the NativeMessageBox methods
  - Pass button strings specified in MesssageBoxOptions to native dialog boxes correctly
  - Use modern TaskDialog on Windows for the native dialog box where available

Ideally, we want to pass shortcut keys to the component to handle, and
only fall back to invoking a menu item if the component was unable to
handle the keyboard event, or if the action was triggered by
clicking/selecting an item in the menu itself. The old implementation
tried to work out whether the action was triggered by a shortcut by
checking the event's characters and modifiers. This method was
inaccurate, because some shortcuts (such as arrow keys) may add
unexpected numpad/function modifier flags.

We now try handling shortcut keys directly in the peer, and pass events
up to the superclass (which will forward them to the main menu) if the
event could not be handled.

This commit also adjusts some Objective-C method signatures to use the
correct string encoding for the BOOL type.

To set a custom host name, add a preprocessor definition for
JUCE_VST_FALLBACK_HOST_NAME.

In cases where internalClickCallback() modified the state of the button this was not being updated until the next call to updateState(). Calling it a second time after the click callback will make sure the state is up to date.