[gfortran] Fix PR19194 : type mismatch between library and compiler

[FX Coudert]

> Bubblestrapped and regtested on i686-pc-linux, John David Anglin comfirmed
> that this fixes all similar errors on hppa64-hp-hpux11.11, but I've not yet
> received confirmation that it also works on mips-sgi-irix6.5.

I'm afraid gfortran doesn't build on mips-sgi-irix6.5 actually (at
least, not out-of-the-box), due to configure problems with complex math
functions (see PR).

If someone knows how to do this, then you may ask him how he fixes the
mentionned problem.

Thanks,
FX