Refactor IBA -- break up unwieldy imagebufalgo.cpp.
Move all high-quality filtered transformations/warps to imagebufalgo_xform.cpp.
Move all drawing and visible annotation to imagebufalgo_draw.cpp.

No actual code or functionality has changed, just moving things from file
to file for better organization and faster recompilation.
Make certain IB constructors explicit.
OpenEXR 2.2 support, esp. for the new DWAA/DWAB compression modes.