note a HeapLang breaking change

CHANGELOG.md

@@ -48,6 +48,10 @@ lemma.
    - Some proofs using lifting lemmas and adequacy theorems need to be adapted
      to ignore the new step counter.
 
+**Changes in `heap_lang`:**
+
+* Rename `Build_loc` constructor for `loc` type to `Loc`.
+
 The following `sed` script helps adjust your code to the renaming (on macOS,
 replace `sed` by `gsed`, installed via e.g. `brew install gnu-sed`).
 Note that the script is not idempotent, do not run it twice.