* common/callback.c (PIPE_BUF): Provide default refinition.
(os_lstat): Use stat if lstat is not available on the host.
(os_ftruncate): Return EINVAL if not available on the host.
(os_truncate): Ditto.
* common/configure.ac: Check for lstat, truncate and ftruncate.
* common/configure: Regenerate.
* common/config.in: Regenerate.