inspect_usage(rdo)rdo, is extracted and
parsed. The usage of each function described in rdo is
obtained also from the actual installed function and compared to the
one from rdo. The return value is a list, with one element for each function usage
as returned by compare_usage1.
One of the consequences of this is that an easy way to add a usage
description of a function, say fu to an existing Rd file is to
simply add a line fu() to the usage section of that file and
run reprompt on it.
inspect_args