Add a mechanism to remove a section from a TOC.
In the CmdRef, the syntax, description, usage notes,
etc. appear in a standalone chapter. Each such chapter
has very similar structure, and many appear on one
page, so having the sub-sections appear in the TOC is
not terribly useful for navigation purposes.
Adding the attribute 'role="notoc"' prevents inclusion
of the section's title in the enclosing TOC.
This doesn't have any effect on the HTML presentation's
navigation pane, just the PDF format's TOC.
A future changelist will apply this feature to the CmdRef.