GD::Graph::mixed graph code

Notes:

A new 'set' value 'types' is used to pass an anonymous list to GD::Graph containing a list of supported graph types.

Dclrs and borderclrs are both given similar but this time, colors. Note that the first graph type, 'area' is given a null 'undef' value in both of these cases. This has the effect of 'hiding' the area graph.