Problems with in-tree host libraries (gmp, ppl, etc)

[Paolo Bonzini]

> 
>> Even then, the ppl configury isn't detecting the gmp we just built.  It
>> seems as though we should install gmp in a local temporary install tree
>> and point ppl at that.  See below for a trace of the ppl configury as it
>> attempts to detect an in-tree gmp (after applying the patch above).
>> AG
> 
> I don't know if ppl was ever setup to detect/use an in-tree gmp.

No, it was not.  So you can drop in gmp/mpfr, or ppl/cloog, but not all
four.

Paolo