unlimit the number of S3method directives

git-svn-id: https://svn.r-project.org/R/trunk@63637 00db46b3-68df-0310-9c12-caf00c1e9a41
be nice to package mosaic

git-svn-id: https://svn.r-project.org/R/trunk@63638 00db46b3-68df-0310-9c12-caf00c1e9a41
tidy up

git-svn-id: https://svn.r-project.org/R/trunk@63640 00db46b3-68df-0310-9c12-caf00c1e9a41
make top-level checks optional, document

git-svn-id: https://svn.r-project.org/R/trunk@63641 00db46b3-68df-0310-9c12-caf00c1e9a41