More debug work, including adding the code tracking throught marked_array for the stack traces, calling into debug when eval has a symbol not defined error (just the first error spot to do this, we can add them all gradually), allowing abort for debug, and adding (exit val) for debug that resumes execution

debug_plans

@@ -0,0 +1,25 @@
+
+
+
+st prints just code
+env prints env, number offset?
+
+argument in variable?
+
+exit with ret value
+	done
+abort
+	done
+
+
+call on error
+	done for eval symbol lookup
+
+
+later
+	u/downp moves
+	print cleanup
+
+
+
+