[merge request] Reverted 'some' and 'program-available'

[Teika Kazura <teika lavabit com>]

Hi. Please merge my branch. It deletes recently adopted functions,
'some' and 'program-available'. They should be, if ever, in librep, not
in Sawfish.

;; usage
(some predicate list)
If any element of LIST is non-nil as the argument of the function
PREDICATE, then returns t.

'Some' can be accepted only if Scheme or Clisp has the same thing.  It
is useful, but any lisp coder can write it in a minute.  Elisp doesn't
seem to have this one.

program-available returns t if the arg is in PATH. But since 
(system cmd) executes cmd in shell, and signals error if impossible,
it seems redundant. 

If it is to be adopted again in librep, then it's better to replace it
with 'which'. (man which doesn't say it's POSIX, so having one may be
good.)

Let me point out that librep lacks file-executable-p.

Thanks,
Teika (Teika kazura)