introduce and use M_LN_2PI

git-svn-id: https://svn.r-project.org/R/trunk@63609 00db46b3-68df-0310-9c12-caf00c1e9a41
did not compile!

git-svn-id: https://svn.r-project.org/R/trunk@63610 00db46b3-68df-0310-9c12-caf00c1e9a41
more reducing exports of methods

git-svn-id: https://svn.r-project.org/R/trunk@63611 00db46b3-68df-0310-9c12-caf00c1e9a41
do not export summary.mlm

git-svn-id: https://svn.r-project.org/R/trunk@63612 00db46b3-68df-0310-9c12-caf00c1e9a41
export quantile.default for now

git-svn-id: https://svn.r-project.org/R/trunk@63613 00db46b3-68df-0310-9c12-caf00c1e9a41