Get the names of arguments in usage sections of Rd objects
Get the names of arguments in usage sections of Rd objects.
All arguments names in the "arguments" section of
extracted. If there is no such section, the results is a character
vector of length zero.
Arguments which have different descriptions for different OS'es are included and not duplicated.
Arguments which have descriptions for a particular OS are included, irrespectively of the OS of the running R process. (todo: introduce argument to control this?)