RFC:Removal of gmp_wrapper.c

Inspired by librandom.jl I have tried to rewrite the gmp interface to avoid gmp_wrapper.c. I can't make it not work on OS X, Ubuntu 32 and 64 bit, but maybe I have missed some memory issues somewhere. I have introduced a limit to the size of the string that can be returned, but it should be easy to change.

See also: #1887 and #2190