Change callback related names so they won't clash with callbacks in other functions.
Change 'null to nil.
Change 'null to nil.
Change to work with the new approach to handling callbacks.
Initial work on getting example15 to work.
Add functions necessary to get examples 1-15 to work.
Enable conversion of 2D lisp arrays to 1D C arrays.
Fix make-pl-pltr-data to properly handle nil grid values. Change pl-callback macro so that it does not automatically define the function using the pl-defcfun macro.
Correct signatures for the plshade functions.
Remove debugging format statements.
Got this example to work again. The plshade() signatures in the PLplot API had changed.
Example16 working.
Example 17 working.
Example 18 working.
Example 19 working.
Example 20 working.