Adds jdbc rake tasks (#5404).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@3721 e93f8b46-1217-0410-a6f0-8f06a7374b81

lib/tasks/jdbc.rake

+# This file was generated by the "jdbc" generator, which is provided
+# by the activerecord-jdbc-adapter gem.
+#
+# This file allows you to use Rails' various db:* tasks with JDBC.
+if defined?(JRUBY_VERSION)
+  require 'jdbc_adapter'
+  require 'jdbc_adapter/rake_tasks'
+end