Add missing requires for the migration helper core.

db/migrate/022_key_constraints.rb

@@ -1,3 +1,5 @@
+require 'lib/migrate'
+
 class KeyConstraints < ActiveRecord::Migration
   def self.up
     # Primary keys

db/migrate/023_add_changesets.rb

@@ -1,3 +1,5 @@
+require 'lib/migrate'
+
 class AddChangesets < ActiveRecord::Migration
   @@conv_user_tables = ['current_nodes',
   'current_relations', 'current_ways', 'nodes', 'relations', 'ways' ]

db/migrate/029_add_user_foreign_keys.rb

@@ -1,3 +1,5 @@
+require 'lib/migrate'
+
 class AddUserForeignKeys < ActiveRecord::Migration
   def self.up
     add_foreign_key :changesets, [:user_id], :users, [:id]

db/migrate/030_add_foreign_keys.rb

@@ -1,3 +1,5 @@
+require 'lib/migrate'
+
 class AddForeignKeys < ActiveRecord::Migration
   def self.up
     add_foreign_key :changeset_tags, [:id], :changesets