Merged r13001 from trunk to 2.5-stable.

Gemfile: pin rake version 10.1.

rake 10.2.0 requires Ruby version >= 1.9.

git-svn-id: http://svn.redmine.org/redmine/branches/2.5-stable@13002 e93f8b46-1217-0410-a6f0-8f06a7374b81