bug#15470: bug in rational numbers in OSX lion

[Junichi Motohisa]

Hi, 

I encountered an error for handling some rational numbers in guile 1.8.8 on OSX 
lion, although it works correctly on CentOS release 6.2 (Final), with guile 
1.8.7. It is something like

guile> (define a 1e-21)
guile> a
1.0e-21
guile> (define a 1e-22)
guile> a
5.36275828919226e-19
guile> (define a 1e-25)
guile> a
6.28575819193153e-19
guile> (define a 1e-26)
guile> a
1.0e-26

My system is as follows.
$ uname -a
Darwin xxx.yyy.hokudai.ac.jp 11.4.2 Darwin Kernel Version 11.4.2: Thu Aug 23 
16:25:48 PDT 2012; root:xnu-1699.32.7~1/RELEASE_X86_64 x86_64

Junichi