This function sets tool tip text that will be used by the next
graphics shape drawn with RSVGTipsDevice. The RSVGTips device "consumes" the tooltip with the first shape that
it draws, e.g., using rect, points, polygon,
etc. If multiple objects are drawn (e.g., by supplying a vector to
points), only the first shape drawn will have a tooltip. Note
that lines does NOT use a tooltip.
Unless sub.special=FALSE, the following special characters in
title, desc, etc. will
be substituted by the XML entity as shown:
The exception to this is that an ampersand followed by lower-case
letters and then a semi-colon is always left alone, because it already
looks like an XML entity.