Add optional docstrings to member descriptors. For backwards

compatibility, this required all places where an array of "struct
memberlist" structures was declared that is referenced from a type's
tp_members slot to change the type of the structure to PyMemberDef;
"struct memberlist" is now only used by old code that still calls
PyMember_Get/Set.  The code in PyObject_GenericGetAttr/SetAttr now
calls the new APIs PyMember_GetOne/SetOne, which take a PyMemberDef
argument.

As examples, I added actual docstrings to the attributes of a few
types: file, complex, instance method, super, and xxsubtype.spamlist.

Also converted the symtable to new style getattr.

Objects/moduleobject.c

@@ -9,7 +9,7 @@ typedef struct {
 	PyObject *md_dict;
 } PyModuleObject;
 
-struct memberlist module_members[] = {
+PyMemberDef module_members[] = {
 	{"__dict__", T_OBJECT, offsetof(PyModuleObject, md_dict), READONLY},
 	{0}
 };