Updating top-level autoconf to 2.59

[Paolo Bonzini]

> Likewise - if building compilers for the same target and multiple hosts it 
> seems at least nonintuitive that --target must be specified for most hosts 
> but must not be specified for the one host that's the same as the target.  
> And will target default to host in that case (if you specify host but not 
> target) for 2.13?

IIRC, the problem is actually specifying --host, not --target.  If you 
configure with just --build --target, it should work right.  Still, I'd 
prefer to not change the semantics of this.

Paolo