[InterNetNews/inn] cc4c9f: Add stub functions for Cancel-Lock when not supported

[Julien ÉLIE]

  Branch: refs/heads/main
  Home:   https://github.com/InterNetNews/inn
  Commit: cc4c9f63f2a48cc5d453b94ad81eaa68b6c70142
      https://github.com/InterNetNews/inn/commit/cc4c9f63f2a48cc5d453b94ad81eaa68b6c70142
  Author: Julien ÉLIE <Julien-Elie at users.noreply.github.com>
  Date:   2022-02-19 (Sat, 19 Feb 2022)

  Changed paths:
    M doc/pod/libinn.pod
    M lib/canlock.c

  Log Message:
  -----------
  Add stub functions for Cancel-Lock when not supported

This way, the function will always be present in libinn.

see #47