feature: expand entity ref (for nextToken())

hi,

when parser is processing DOCDECL parser can encounter possibly
complex entity declarations (such as containing embedded markup),
there are tow cases:
1) when entity ref is encountered by next() will be nicely expanded
2) however for nextToken() then only thing we currently do is to report
entity reference (with name) and skip any expansion. as this is not
what we may want when processing document with more complex
entities i have just added an optional feature to allow requesting
expanding entity references by nextToken().

comments?

alek