Weakref 0.3.3

• Restore dtors to prevent crash in multi-requests scenario

Weakref 0.3.2

• Fix crash in wr_store_tracked_object_dtor

Weakref 0.3.1

• Fix a bug where acquired ref would be dtored before the wref during shutdown (#69131)

Weakref-0.3.0

• Support PHP7 (Big thanks to Julien Pauli for helping with the upgrade) (issue #19)
• Add support for cloning WeakMap
• Iterating WeakMap now yields objects as keys (issue #17)