Update doc/reference submodule
Update doc/reference submodule

In particular this pulls in an update to the auto-deref
recursion_limit example, to no longer rely on the Freeze query.

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