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

- 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

The comment at the top of reaper_plugin_fx_embed.h specifies that the
'index' parameter for the embedded UI feature will always be set to
effEditDraw.

See BREAKING-CHANGES.txt for more details.

This prevents test failures in the Steinberg VST3 validator.

This reverts commit 271e66fbed.

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