This function returns a color.
The color is the sum of the specular reflection for all the light sources
multiplied by the co-efficient Ks and the highlight color HI.

This must be a float.  Defaults to 1.0.
This is the co-efficient for the specular function.
It controls the intensity of the returned color.
For best results Ks should range from [0,1].

This must be a color.  Default is white.
This is the color of the highlight on the surface.
It tints the color returned from the specular function.

This must be a float.
This controls the falloff rate of the specular highlights.
This larger Ns is the larger the size of the highlights.

This must be a vector.  The default is state->normal.
This is the normal to the surface point to be shaded.

This must be a vector.  The default is the state->dir.
This is the vector from the camera to the surface point to be shaded.

This function returns a color.  
The color is the sum of the specular reflection for all light sources
multiplied by the co-efficient Ks and the highlight color HI.