Optimize committers/users map retrieval for statistic graphs (#13487).

git-svn-id: http://svn.redmine.org/redmine@13361 e93f8b46-1217-0410-a6f0-8f06a7374b81
Fix syntax for ruby 1.8.7 (#13487).

git-svn-id: http://svn.redmine.org/redmine@13362 e93f8b46-1217-0410-a6f0-8f06a7374b81