First set of ported octave-forge functions

[John W. Eaton]

On 17-Jul-2007, David Bateman wrote:

| Find attached the first set of octave-forge functions from my list that
| I ported. It includes the functions meshc, peaks, brighten, autumn,
| bone, cool, copper, hot, hsv, jet, pink, prism, rainbow, spring, summer,
| white and winter. It also documents these functions in the manual.
| 
| Overall there were minimal changes to these functions in porting them. I
| 
| * Changed the copyrights to the Octave version of the GPL header
| * Used print_usage() rather than usage(...)
| * A few minor texinfo help string changes
| * Allowed the brighten function to also accept a graphics handle.
| 
| Note that there are a couple of additional changes in this patch.
| Firstly the brighten function should be able to change the colormap of
| surfaces plotted with mesh, etc. However, the __go_draw_axes__.m
| function uses a fixed colormap for surfaces. With gnuplot 4.2 or later
| it should be possible to fix the colormap to an arbitrary map, and so I
| added the code for this. I can't test it however as I have gnuplot 4.0
| and not 4.2.
| 
| I also removed the colormap setting from the ocean.m and gray.m
| functions. Matlab requires that the colormap function is explicitly
| called on the maps like "colormap(summer())" to set the map, and so the
| removal was for compatibility with matlab and to the ported functions.

Please check in these changes.

Thanks,

jwe