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

[FX Coudert]

>> This patch adds support for -ffpe-trap on systems with SysV
>> fpsetmask() function. This includes solaris, (free|net|open)bsd, hpux
>> and irix. When that one is in, I'll work on support for darwin and
>> AIX, and then we'll have most platforms covered.
> 
> This new version of the patch adds support for AIX. Regtested on 
> i686-linux, tested on i386-freebsd4.8 and sparc-solaris (for SysV), and 
> AIX (thanks to David Edelsohn!).
> 
> OK for mainline?

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