add table.bigint support

In the DSL you can now do:

create_table(:foos) do |t|
  t.bigint :hi
end

activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb

@@ -270,7 +270,7 @@ module ActiveRecord
         @columns_hash.delete name.to_s
       end
 
-      [:string, :text, :integer, :float, :decimal, :datetime, :timestamp, :time, :date, :binary, :boolean].each do |column_type|
+      [:string, :text, :integer, :bigint, :float, :decimal, :datetime, :timestamp, :time, :date, :binary, :boolean].each do |column_type|
         define_method column_type do |*args|
           options = args.extract_options!
           column_names = args

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -94,6 +94,7 @@ module ActiveRecord
         int8range:   { name: "int8range" },
         binary:      { name: "bytea" },
         boolean:     { name: "boolean" },
+        bigint:      { name: "bigint" },
         xml:         { name: "xml" },
         tsvector:    { name: "tsvector" },
         hstore:      { name: "hstore" },

activerecord/test/cases/migration/change_schema_test.rb

@@ -97,6 +97,25 @@ module ActiveRecord
         end
       end
 
+      def test_create_table_with_bigint
+        connection.create_table :testings do |t|
+          t.bigint :eight_int
+        end
+        columns = connection.columns(:testings)
+        eight   = columns.detect { |c| c.name == "eight_int"   }
+
+        if current_adapter?(:OracleAdapter)
+          assert_equal 'NUMBER(8)', eight.sql_type
+        elsif current_adapter?(:SQLite3Adapter)
+          assert_equal 'bigint', eight.sql_type
+        else
+          assert_equal :integer, eight.type
+          assert_equal 8, eight.limit
+        end
+      ensure
+        connection.drop_table :testings
+      end
+
       def test_create_table_with_limits
         connection.create_table :testings do |t|
           t.column :foo, :string, :limit => 255