Simplify Solaris configuration

[Eric Botcazou]

> The patch allowed a sparcv9-sun-solaris2.11 bootstrap to run well into
> building the target libraries (failed configuring libgfortran since I'd
> mis-merged the 32-bit and 64-bit gmp.h), a sparc-sun-solaris2.10
> bootstrap is still running.
>
> I'll probably fix the gmp.h issue, rebuild the sparcv9-sun-solaris2.11
> configuration and commit unless I find problems or you disapprove of the
> approach.

No, this is fine by me, thanks.

-- 
Eric Botcazou