simplification in R_mpfr_nr_limbs()


git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rmpfr@202 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
move the "internal printing" of NA,NaN,Inf to lowlevel.R (where there is no .Rout.save)

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rmpfr@203 edb9625f-4e0d-4859-8d74-9fd3b1da38cb