The *.fig files need to be converted to .png and .eps using:
    fig2dev -L png <filename>.fig <filename>.png
    fig2dev -L eps <filename>.fig <filename>.eps

The resulting images are used by doxygen when it encounters descriptions like:
    /**
     ...
	 * @image html fig_grid.png
	 * @image latex fig_grid.eps
     */

...in source files (this example is from "maths/GridOnSphere.h").

Currently the CMake build system does not setup rules for this since
there's only two places these images are used.

If images get used more in the future then we can add rules to cmake by
creating a FindFig2dev.cmake module and adding rules using ADD_CUSTOM_COMMAND(), etc.

Fig2dev has Mac OS X and Windows binaries at:
http://tams-www.informatik.uni-hamburg.de/applets/jfig/download.html
