goo bignums

i've made available goo v0_155 on http://www.googoogaga.org which 
offers bignum support by way of gmp:

   http://www.swox.com/gmp/

this fixes the float reading bug reported by chris double.  many thanks 
to james knight for his help in writing the original gmp interface 
code.  i have yet to test this release on windows but assume it should 
at least work fine within a gmp augmented cygwin.  bignums are strictly 
an add on module, and as such can be turned off by rebuilding with the 
``(use goo/bignum)'' form commented out from eval/main.goo.

i also took this as an opportunity to improve goo's c embedding 
facility to support their use within macros.  i've sketched this out in

   http://www.jbot.org/Projects/goox-intro.html

jonathan