Build using --with-gmp and shared libraries

[Paolo Bonzini]

>It's something that we want, together with an in-tree gmp (mpfr depends on gmp
>after all).  There were some past conversations about this, and I remember
>having been told that at least one gcc heavyweight had failed doing this due to
>some weirdness either in gmp or mpfr.  I'm cc'ing Paul Brook as I think that I
>got that information from him.
>  
>
I don't remember that, but the toplevel has improved in functionality in 
order to support toplevel bootstrap.  It should be much much easier to 
do that now, and even to optionally bootstrap gmp/mpfr with the in-tree 
compiler (yay!).

Paolo

ps: if any "uberbaum heavyweight" is reading this, and can approve 
toplevel patches, let me remember the toplevel has an important bug 
fixed by http://gcc.gnu.org/ml/gcc-patches/2005-11/msg00380.html