parse_Rdtext(text, section = NA) If section is given, then parse_Rdtext parses
text as appropriate for the content of section section.
This is achieved by inserting text as an argument to the TeX
macro section. For example, if section is
"\usage", then a line "\usage{" is inserted at the
begiinning of text and a closing "}" at its end.
If section is NA then parse_Rdtext parses it without
preprocessing. In this case text itself will normally be
a complete section fragment.
parse_Rdpiece