Fwd-port: Add a missing changelog entry back from 0.2.4.11-alpha

When I merged the fix for #7351, and implemented proposal 214 (4-byte
circuit IDs), I forgot to add a changes file.  Later, we never noticed
that it didn't have one.

Resolves ticket #11555.  Thanks to cypherpunks for noticing this was
missing.

This is a cherry-pick of 75e10f58a97f051f7d8576f96c2e32fcb2f07ade into
the master branch.