There is a module file gmp.lsp to import libgmp.so or libgmp.dylib in:
http://newlisp.org/downloads/development/gmp.lsp
At the moment gmp.lsp tries to load only libgmp.so or libgmp.dylib. I will add a load line for libgmp.dll on the weekend when I can test on MS Windows.
In this first version the file contains import for integer functions only. Floats will be added at a later time. Precision is set to 2048 decimal digits by default but can be changed to any number higher than that.
See the header of the file for details of functions supported and link to the GMP website.
Lutz