Render the flipped columns in reverse order
Render the flipped columns in reverse order

This completes the per-image flip implementation. Tile bounds are
re-positioned within the image. When rendering, the x ordinals are
remapped to the flipped ones.

To use, set "flipped" on the image instead of the viewer. The code
is compatible with rotations and wrapping.

Implements #1553

openseadragon/openseadragon,openseadragon/openseadragon