Git commits in Moodle 2.5.5 by Oleg Sychev

commit 64ab5badbfbc156679c9b77bbd51eb6f07f22b68
Author: Oleg Sychev <oasychev@gmail.com>
Date:   Sat, 25 Jan 2014 07:41:01 +0800
Tag:    v2.5.5

MDL-42456: add Mercurial vcs support to plugin_external_source