add [<- and [[<- overrides for S4 data.frames, since the S3 methods corrupt the class, and reimplement the $<- override using S3Part() for consistency

git-svn-id: https://svn.r-project.org/R/trunk@67058 00db46b3-68df-0310-9c12-caf00c1e9a41
support primitives in callGeneric()

git-svn-id: https://svn.r-project.org/R/trunk@67059 00db46b3-68df-0310-9c12-caf00c1e9a41