RFR: CODETOOLS-7901950: jcheck does not work with Mercurial 4.1

[Erik Joelsson]

The way a Mercurial plugin interacts with Mercurial has changed over 
time. The technique used in jcheck and defpath has been deprecated for a 
while and in 4.1, it no longer works.

I have a patch that adopts the new method using decorators, introduced 
in Mercurial 1.9. It also contains a fallback workaround that keeps 
compatibility with older versions.

Bug: https://bugs.openjdk.java.net/browse/CODETOOLS-7901950

Webrev: 
http://cr.openjdk.java.net/~erikj/CODETOOLS-7901950/jcheck-webrev.01/


I have the same changes ready for defpath which doesn't have it's own 
component in Jira.

Webrev: 
http://cr.openjdk.java.net/~erikj/CODETOOLS-7901950/defpath-webrev.01/

/Erik