jcheck review request - hg 2.9 compatibility

[John Coomes]

John Coomes (John.Coomes at oracle.com) wrote:
> The localrepo.branchtags() method was removed in hg 2.9-rc; use
> branchmap() instead when available.
> 
> http://cr.openjdk.java.net/~jcoomes/tools/jcheck/compat-branchtags/

Anyone willing to take a look?  It's pretty small.

hg 2.9 will be out in a couple of days; I'd like to push tomorrow.

-John