Clarify that fragid support is optional when parse=text

We agreed to clarify that fragid support is optional when parse=text.
I think the best way to do that is to make fragid support optional for
all media types. See:

https://ndw.github.io/xinclude/xinclude/xinclude11/head/diffcr.html#xpointer-and-fragid

                                        Be seeing you,
                                          norm

-- 
Norman Walsh
Lead Engineer
MarkLogic Corporation
Phone: +1 512 761 6676
www.marklogic.com