5f7ad995af introduced an issue where the
string of external libraries would be escaped in one go. This is
incorrect, because only the individual paths should be escaped. The
semicolons separating each path should not be escaped.

Without the BOM, VS assumes UTF-8 strings (subproject file names etc.)
are ansi-encoded.

AU and AUv3 plugins only support version numbers with up to 3 parts.

- 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

When loading exporter icons on a background save thread we need to take the MessageManagerLock as the image file may be an SVG which has a message thread dependency in the Drawable parsing code

See BREAKING-CHANGES.txt for more details.

This fixes warnings that are emitted when building with the `-analyze`
flag enabled.