[gfortran,patch] -ffpe-trap library support for SysV

[François-Xavier Coudert]

> Not OK for FreeBSD.  I need to look into the details,
> but fpsetmask has been deprecated in FreeBSD and new
> code is suppose to use the fenv(3) facilities.  Off
> hand, I do not remember the version of FreeBSD when
> the change was made.

Well, this is not hardcoded as the solution for FreeBSD. The configury
just checks for fpsetmask, and if it's there, uses it. So I guess that
should not be a problem.

As for fenv (it's already been discussed here), there's no C99 way to
raise FPE on individually selected exceptions.

FX