- New UI element: the "Curve Button".

For mapping ranges (like 0 - 1) to another range, the curve button can be
used for proportional falloff, bone influences, painting density, etc.
Most evident use is of course to map RGB color with curves.

To be able to use it, you have to allocate a CurveMapping struct and pass
this on to the button. The CurveMapping API is in the new C file
blenkernel/intern/colortools.c
It's as simple as calling:

curvemap= curvemapping_add(3, 0, 0, 1, 1)

Which will create 3 curves, and sets a default 0-1 range. The current code
only supports up to 4 curves maximum per mapping struct.
The CurveMap button in Blender than handles allmost all editing.
Evaluating a single channel:

float newvalue= curvemapping_evaluateF(curvemap, 0, oldval);

Where the second argument is the channel index, here 0-1-2 are possible.
Or mapping a vector:

curvemapping_evaluate3F(curvemap, newvec, oldvec);

Optimized versions for byte or short mapping is possible too, not done yet.

In butspace.c I've added a template wrapper for buttons around the curve, to
reveil settings or show tools; check this screenie:

http://www.blender.org/bf/curves.jpg

- Buttons R, G, B: select channel
- icons + and -: zoom in, out
- icon 'wrench': menu with tools, like clear curve, set handle type
- icon 'clipping': menu with clip values, and to dis/enable clipping
- icon 'x': delete selection

In the curve button itself, only LMB clicks are handled (like all UI elements
in Blender).

- click on point: select
- shift+click on point: swap select
- click on point + drag: select point (if not selected) and move it
- click outside point + drag: translate view
- CTRL+click: add new point
- hold SHIFT while dragging to snap to grid
(Yes I know... either one of these can be Blender compliant, not both!)
- if you drag a point exactly on top of another, it merges them

Orange branch: OpenEXR finally in Blender!

Credits go to Gernot Ziegler, who originally coded EXR support, and to
Austin Benesh for bringing it further. Kent Mein provided a lot of code
for integrating float buffers in Blender imbuf and ImBuf API cleanup,
and provided Make and Scons and static linking.

At this moment; the EXR libraries are a *dependency*, so you cannot get
the Orange branch compiled without having OpenEXR installed. Get the
(precompiled or sources) stuff from www.openexr.com. Current default is
that the headers and lib resides in /user/local/

Several changes/additions/fixes were added:

- EXR code only supported 'half' format (16 bits per channel). I've added
float writing, but for reading it I need tomorrow.
- Quite some clumsy copying of data happened in EXR code.
- cleaned up the api calls already a bit, preparing for more advanced
support
- Zbuffers were saved 16 bits, now 32 bits
- automatic adding of .exr extensions went wrong

Imbuf:

- added proper imbuf->flags and imbuf->mall support for float buffers, it
was created for *each* imbuf.
- found bugs for float buffers in scaling and flipping. Code there will
need more checks still
- imbuf also needs to be verified to behave properly when no 32 bits
rect exists (for saving for example)

TODO:

- support internal float images for textures, backbuf, AO probes, and
display in Image window

Hope this commit won't screwup syncing with bf-blender... :/