RFR (jaxp) 8136778: SAXParser: support stopping a parsing process

[huizhe wang]

Hi,

This is an enhancement to allow a SAX parsing process to be stopped and 
resumed. A SAX process scans through an entire document while making 
callbacks to its handler when defined events are met. The stop and 
resume methods make it easy to stop and subsequently resume the process 
as needed. Until now, the parsing process can only be stopped brutally 
by throwing an Exception.

JBS: http://ccc.us.oracle.com/8136778
Webrev: http://cr.openjdk.java.net/~joehw/jdk9/8136778/webrev/

Thanks,
Joe