scm: mercurial: switch rev parameter of extension rhlog() if above Mercurial 1.6 or not (#9465)
On Mercurial 1.5, following error raises.
<pre> hg --config extensions.redminehelper=lib/redmine/scm/adapters/mercurial/redminehelper.py \ --rhbranch default --from default --to 0
abort: unknown revision '"default"'! </pre>
Authored by: tmaruyama 2011-10-24
Parent: [r7640]
Child: [r7642]
