Reorder AllocationDefinedness members
Reorder AllocationDefinedness members

This improves the clarity of the documentation a bit since they can
reference each other when reading the member docs in sequence.

aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust