[Q] Refactor out sequence-oriented builtins from fns.c to the new sequence.c.

[Stephen J. Turnbull]

QUERY

Aidan Kehoe writes:
 > 
 > Actual changeset is compressed and attached, for the sake of avoid a 500k
 > mail. The changelog and commit message is in plain text.
 > 
 > # HG changeset patch
 > # User Aidan Kehoe <kehoea at parhasard.net>
 > # Date 1323024170 0
 > # Node ID 1a507c4c6c42c6bc3afdd33bffcbaa14dbd88b62
 > # Parent  7c383c5784edcea0694661cfebd7ae4e613d7e7b
 > Refactor out sequence-oriented builtins from fns.c to the new sequence.c.

Have you considered whether our code varies enough from GNU that
future synchs of the sequence code won't be impaired by this change
(ie, they would have to be done by hand anyway?)