fxbit-set? has a new definition

[Gwen Weinholt]

The errata for R6RS corrects the definition of fxbit-set? in this way:

#|
In the specification of fxbit-set?, the sentence

"Fx2 must be non-negative and less than (fixnum-width)."
should be replaced by

"Fx2 must be non-negative."
Also, the code describing its computation should be changed to:

(if (fx>= fx2 (fx- (fixnum-width) 1))
    (fxnegative? fx1)
    (not
      (fxzero?
         (fxand fx1
                (fxarithmetic-shift-left 1 fx2)))))
|#

Ikarus still uses the old definition and raises an exception if fx2 is (fixnum-width) or greater.