=Draw Module Fixed=

This commit fixes the Draw module.  All buttons/widgets created via the Draw
module in a SpaceScript area are now inserted into a global list attached to
the SpaceScript data.  This list is cleared before each draw, when freeing
the space, and when the area is switched to another space.c

This is necessary to prevent Blender's internal UI code from getting invalid
pointers to python data.  In addition, it allows storing widget tooltips
inside the python Button objects, which solves that little bit of stupidity.

Note that this reverts the previous weaklist solution.  In fact, I had to go
over each previous commit by Campbell after this code originally branched
before the weaklist commit and re-add each commit.  So if anything is
missing, just tell me, or feel free to re-add it.

source/blender/python/BPY_extern.h

@@ -51,6 +51,25 @@ struct bPythonConstraint; /* DNA_constraint_types.h */
 extern "C" {
 #endif
 
+	/*These two next functions are important for making sure the Draw module
+	  works correctly.  Before calling any gui callback using the Draw module,
+	  the following code must be executed:
+	  
+		if (some_drawspace_pylist) {
+			BPy_Set_DrawButtonsList(some_drawspace_pylist->but_refs);
+			BPy_Free_DrawButtonsList();
+		}
+		some_drawspace_pylist = PyList_New(0);
+		BPy_Set_DrawButtonsList(some_drawspace_pylist);
+
+      Also, BPy_Free_DrawButtonsList() must be called as necassary when a drawspace
+      with python callbacks is destroyed.
+      
+      This is necassary to avoid blender buttons storing invalid pointers to freed
+      python data.*/
+	void BPy_Set_DrawButtonsList(void *list);
+	void BPy_Free_DrawButtonsList(void);
+	
 	void BPY_pyconstraint_eval(struct bPythonConstraint *con, float ownermat[][4], float targetmat[][4]);
 	void BPY_pyconstraint_settings(void *arg1, void *arg2);
 	int BPY_pyconstraint_targets(struct bPythonConstraint *con, float targetmat[][4]);