Ignore BOMs

Hello,

In response to recent email and XML.com Slack conversations about BOMs,
two proposals:

* Proposed erratum: if a UTF-8 grammar begins with a BOM, the BOM must
  be ignored[1]
* Invisible XML parsers should ignore a BOM on UTF-8 inputs[2]

                                        Be seeing you,
                                          norm

[1] https://github.com/invisibleXML/ixml/issues/174
[2] https://github.com/invisibleXML/ixml/issues/175

--
Norm Tovey-Walsh
Saxonica