title: do not show function help document in building R package by roxygen2
body: <p>I am using <code>devtools</code> to build R package, and there are some functions that are NOT designed to be visible to end-users. However, since these functions involve calling C codes by <code>.Call</code>, so that I have to write <code>@useDynLib</code> above the function for automatic generation of .Rd files. In that way, when I build the package, even I did NOT include the <code>@export</code> for those functions, they nonetheless appear in the help document... Is there a way to <strong>suppress</strong> those functions even if they have been documented? Thanks!</p>