typo in r185

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rmpfr@186 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
update to  log1pexp() {and two typos: ")", "."}

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rmpfr@187 edb9625f-4e0d-4859-8d74-9fd3b1da38cb