fx+/carry with non-fixnum segfaults

[Gwen Weinholt]

The irritants from fx+/carry are wrong, and some of them cause segfaults when printed:

Ikarus Scheme version 0.0.4-rc1+ (revision 1844, build 2009-08-03)
Copyright (c) 2006-2009 Abdulaziz Ghuloum

> (fx+/carry (+ (greatest-fixnum) 1) 1 0)
Unhandled exception
 Condition components:
   1. &assertion
   2. &who: -
   3. &message: "not a number"
   4. &irritants: ((#<constant rtd> . 536870912))
> (fx+/carry (* 1000 (greatest-fixnum) ) 1 0)
Unhandled exception
 Condition components:
   1. &assertion
   2. &who: -
   3. &message: "not a number"
   4. &irritants: ((31 . #<procedure #<unknown>>))
> (fx+/carry (* 10000 (greatest-fixnum) ) 1 0)
Unhandled exception
 Condition components:
   1. &assertion
   2. &who: -
   3. &message: "not a number"
   4. &irritants:
Segmentation fault (core dumped)

Ikarus Scheme version 0.0.4-rc1+, 64-bit (revision 1844, build 2009-08-03)
Copyright (c) 2006-2009 Abdulaziz Ghuloum

> (fx+/carry (+ (greatest-fixnum) 1) 1 0)
Unhandled exception
 Condition components:
   1. &assertion
   2. &who: -
   3. &message: "not a number"
   4. &irritants:
Segmentation fault (core dumped)

[Abdulaziz Ghuloum (aghuloum)]

Fixed in 1845. Thanks!