Reimport c-list from upstream. It allows iterating over const-list. Upstream commit is 17e7781b3fe26e06bbe3817e8ed7418d80f63feb "build: update NEWS".
Include the circular, doubly-linked list implementation from c-util/c-list [1], commit 864051de6e7e1c93c782064fbe3a86b4c17ac466. [1] https://github.com/c-util/c-list