[Rd] Documentation: pls add xref from "sum" to "rowSums" (PR#11145)

[mike.prager at noaa.gov]

Full_Name: Mike.Prager
Version: 2.6.2
OS: Windows XP Prof + SP2
Submission from: (NULL) (192.154.40.252)


Please add a cross-reference in R help files from "sum" to "rowSums" and also
from "mean" to "rowMeans".

Reasons: (1) New users may not be aware of rowSums, etc., and the simple
functions will be their points of entry to the help files.  (2) Even old users
can't remember everything (or sometimes, much of anything).

Thanks for considering it!