[gfortran,patch] Fix code generated for NINT

[FX Coudert]

> Does Cygwin comply? I am just about to launch a regtest.  I am only  
> asking because the consequences of the NINT bug are particularly  
> dire. :-)

Yes, I know. I have lots of code myself which will probably get a  
large hit in performance due to that patch, and I was really  
reluctant to do it for such a simple case, but I can't find another  
way of fixing it :(

Oh, and by the way, a cygwin test can only help, though I think it  
has lround.

FX