changing gmp install name

[Jason Moxham]

Here is the next attempt

http://217.35.81.229/gmp/gmp_plus.html

NOTE: It should be consider experimental , and installing may (but
hopefully not) cause problems for any existing gmp installation. see
README_gmp_plus

I've added high(basecase) and low(basecase and recursive) part multiplica=
tion=20
, and attempted to tune the parameters with the gmp tuneup , although I t=
hink=20
that I've got the tuneup parameters and method wrong

Jason