Sequence functions

[Earl A. Killian <EAK at MIT-MC>]

Using subseq instead of additional arguments is of course what
other languages do, and it is quite tasteful in those languages
because the creating a subsequence doesn't cons.  In Lisp it
does, which makes a lot of difference.  Unless you're willing to
GUARENTEE that the consing will be avoided, I don't think the
proposal is acceptable.  Consider a TECO style buffer management
that wanted to use string-replace to copy stuff around; it'd be
terrible if it consed the stuff it wanted to move!