The value of xcmFontIndex corresponding to the xcmFontEntry
which represents the default font for this Interpreter.
A value of (-1) means 'other'.
A value of (-2) means 'unknown'.
A value of (-3) means 'notPresent'.
A value of 'other' (-3) should be used for those
interpreters which have no default font (e.g. PostScript).
For agents that choose not to implement the Resources MIB,
this object specifies the ID of the default font. This use
of this object is significant only to the specific product.