Towards 0.5.4.
Fix #897: Deserialization from 050 to 053 crashes optimizer.
Fix #899: Always unbox arguments to reflective calls.
Merge pull request #900 from sjrd/fix-deserialize-hack-050-to-053

Fix #897: Deserialization from 050 to 053 crashes optimizer.
Merge pull request #901 from sjrd/unbox-args-of-refl-calls

Fix #899: Always unbox arguments to reflective calls.