Remove old host cases from toplevel configure

[Paolo Bonzini]

On 03/24/2011 03:11 PM, Joseph S. Myers wrote:
> Furthermore, the whole idea of the toplevel configure tentative_cc
> setting code is dubious since this is an autoconf-generated script and
> it's autoconf's job to deal with finding a working compiler, putting
> it in ANSI C mode, etc. - so if someone did wish to resupport one of
> these hosts (and in the unlikely event that building current tools
> using the old system compiler is at all possible) it would be better
> to put system-specific pieces in autoconf and make toolchain configure
> code work using features not host triplet tests as far as possible.

100% agreed, I've meant to clean this up for a long time.

> OK to commit?

Yes, thank you very much.

Paolo