[Bug libstdc++/47913] [C++0x] improve ratio_add to overflow less often

[marc.glisse at normalesup dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47913

--- Comment #10 from Marc Glisse <marc.glisse at normalesup dot org> 2011-03-02 
11:53:58 UTC ---
Created attachment 23512
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=23512
avoid denominator overflows (untested)