In order to make the doc checker doclet capable of generating a report
on the number and type of errors and warnings, need to make available to
the doclet API:

- The error messages that @see generates, such as "class xx doesn't exist"
- The warning messages that @see generates, such as
   javadoc: warning - java.applet.Applet.isActive(): Tag @link: missing #: "start()"

These should be accessed by different methods, so they
can be documented at different levels of priority, say getSeeErrors()
and getSeeWarnings()