RFR: (jaxp) 8003261 : static field is public but not final

[Joe Wang]

Hi,

This is the 2nd of the three [findbug] issues. The field fVersion is 
simply made final.

webrev:
http://cr.openjdk.java.net/~joehw/jdk8/8003261/webrev/

Test:
No new test needed.

Thanks,
Joe