Suggested change: Allow nesting of <EMPH> tags

example:
<EMPH RENDER="bold">Collection of <EMPH RENDER="italic">cartes des
visites</EMPH> formed in the 1950s by John Doe</EMPH>

Rationale:
To simplify the use of EMPH tags when more than one kind of emphasis is required within a
single passage of text. With the Beta version of the DTD, the above example would have
required the following tags:

<EMPH RENDER="bold">Collection of </EMPH>
<EMPH RENDER="bolditalic">cartes des visites</EMPH>
<EMPH RENDER="bold"> formed in the 1950s by John Doe</EMPH>