This is the only build breaking change to our juce branch now (singe MIDI note names got added). Would be good to see it added 
/** Returns a transform that will flip coordinates horizontally within a window of the given width.
*/
static AffineTransform horizontalFlip (float width) noexcept;
AffineTransform AffineTransform::horizontalFlip (float width) noexcept
{
return { -1.0f, 0.0f, width,
0.0f, 1.0f, 0.0f };
}