[Bug-mit-scheme] "bin" file incompatibility, confusing error comment

[gjs]

Description:
It seems that sf across C vs native backends produces incompatible bin
files.  Worse, the error comment when trying to load such incompatible
files is very unfortunate.  This is all on 64-bit linux (specifically
Sussman's laptop).

To reproduce:
Produce some innocent file foo.scm.  Then start up two Schemes,
scheme A, which compiles to C:

Image saved on Thursday April 30, 2009 at 12:19:48 AM
  Release 7.7.90.+ || Microcode 15.1 || Runtime 15.7 || SF 4.41 || LIAR/C 4.118
  Edwin 3.116      || SOS 1.8        || IMAIL 1.21

and scheme B, which compiles to native code:

Image saved on Friday May 1, 2009 at 4:50:19 PM
  Release 7.7.90.+ || Microcode 15.1 || Runtime 15.7 || SF 4.41 || LIAR/i386 
4.118
  Edwin 3.116      || SOS 1.8        || IMAIL 1.21


Compile foo in Scheme A, and test its bin file

(cf "foo")
(pp (fasload "foo.bin"))
;Loading "foo.bin"... done
(begin (define (mumble) 2) (define (grumble) 3))
;Unspecified return value

Looks good.  Now try reading the same bin file in Scheme B

(pp (fasload "foo.bin"))
;Loading "foo.bin"... 
;Attempt to read binary file "/home/gjs/metacirc/axch-thesis/foo.bin" failed: 
either it's not binary or the wrong version.
;To continue, call RESTART with an option number:
; (RESTART 1) => Return to read-eval-print level 1.
;Start debugger? (y or n): 

That's unfortunate; but if it is necessary, then so be it.
But now, compile the same file in Scheme B and test the bin:

(cf "foo")
(pp (fasload "foo.bin"))
;Loading "foo.bin"... done
(begin (define (mumble) 2) (define (grumble) 3))
;Unspecified return value

Works.  But now, try reading that same file in Scheme A:

(pp (fasload "foo.bin"))
;Unable to find file "foo.bin" because: File does not exist.
;To continue, call RESTART with an option number:
; (RESTART 1) => Return to read-eval-print level 1.
;Start debugger? (y or n): 

OOPS!  Not only does it fail to load, which is unfortunate, but the
error comment is also very dis-informative, in that the file does
exist, it was just produced by the wrong sf.

GJS, channeling axch