new .mpfr.gmp.numbbits(); .mpfr.erange.set() instead of `.mpfr.erange<-` which never worked

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rmpfr@193 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
fix buglet in "mpfr1" validity function


git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rmpfr@194 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
.mpfr1list() & experimental mpfrXport()

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rmpfr@195 edb9625f-4e0d-4859-8d74-9fd3b1da38cb