ai_19_2 released

road graphics adjusted
road code adjusted, code now bug free
road code includes a fast path finder (sets of pointers to virtual structures, see road.h) . This code is also the first part of unit movement (getting there!).
road code added to connect fort to closest town
(just to test...later towns will connect to each other)
adjusted graphics thanks to er-no:
desert hill
desert plain
adjusted graphics (dunes) to integrate er-no's graphics.
added graphics: plain oasisx5, oasis forestx5
added code to oasis to generate forests
added code to oasis to use separate plains.
adjusted hills on oasis to be dunes.
adjusted hill graphics on temp worlds.
other code adjustments, including debugging a memory leak in various nodes.
added er-no to temporary credits (planet names).