#3 Enumerated attribute types allow commas

[Matt Olsen]

In the DTD when defining attributes for an element,
psgml will allow commas in between enumerated types
when in XML mode.

For example:
<!ELEMENT DOC (TITLE, PARA+)>
<!ATTLIST DOC MODSTAT (ADD, DELETE, REPLACE) #IMPLIED>
is allowed when it should be:
<!ELEMENT DOC (TITLE, PARA+)>
<!ATTLIST DOC MODSTAT (ADD | DELETE | REPLACE)
#IMPLIED>