CakeML:61fff9792e0238dffe0b37822eac882a89bcf495 Update for deletion of Dtype and Dexn from flatLang #1305 (flatdec) Merging into:77cbb88a69527fe7eb542f5aa746cc11f57b21e4 Remove some unnecessary proof obligations from CF (#1310) HOL:4bbb1ec36b9701b9273024276cb31821e6043f6b Merge pull request #1791 from HOL-Theorem-Prover/ty_sub_change