Core and builtins
+- Fixed two bugs reported as SF #535905: under certain conditions,
+ deallocating a deeply nested structure could cause a segfault in the
+ garbage collector, due to interaction with the "trashcan" code;
+ access to the current frame during destruction of a local variable
+ could access a pointer to freed memory.
+
- The optional object allocator has been enabled by default.
- If you try to pickle an instance of a class that has __slots__ but