Translate ORA-00060 into ActiveRecord::Deadlocked error

This PR translates `ORA-00060` into `ActiveRecord::Deadlocked` error.

Added an `ORA-00060` reproduction test case equivalent to
activerecord/test/cases/adapters/mysql2/transaction_test.rb.
https://github.com/rails/rails/blob/8f2490b57f488ed60fc6e0a201ccd5e66811ab51/activerecord/test/cases/adapters/mysql2/transaction_test.rb#L36-L61

The following is a reproduce testing log.

```console
% bundle exec rspec ./spec/active_record/connection_adapters/oracle_enhanced_adapter_spec.rb:575
(snip)

  1) OracleEnhancedAdapter Transaction Raises Deadlocked when a deadlock
  is encountered
     Failure/Error:
              expect {
                barrier = Concurrent::CyclicBarrier.new(2)

                t1 = TestPost.create(title: "one")
                t2 = TestPost.create(title: "two")

                thread = Thread.new do
                  TestPost.transaction do
                    t1.lock!
                    barrier.wait

       expected ActiveRecord::Deadlocked, got
       #<ActiveRecord::StatementInvalid: OCIError: ORA-00060: deadlock
       detected while waiting for resource: UPDATE "TEST_POSTS" SET
       "TITLE" = :a1 WHERE "TEST_POSTS"."ID" = :a2> with backtrace:
```

And this commit resolves `Java::JavaSql::SQLException` exception.
`Java::JavaSql::SQLException` is not `NativeException`.

https://travis-ci.org/rsim/oracle-enhanced/jobs/301301765

It seems to be a potential issue caused by not passing test
`OracleEnhanced::JDBCConnection#error_code` in rails/activerecord tests.

lib/active_record/connection_adapters/oracle_enhanced/jdbc_connection.rb

@@ -460,6 +460,8 @@ def error_code(exception)
           case exception
           when NativeException
             exception.cause.getErrorCode
+          when Java::JavaSql::SQLException
+            exception.getErrorCode
           else
             nil
           end

lib/active_record/connection_adapters/oracle_enhanced_adapter.rb

@@ -672,6 +672,8 @@ def translate_exception(exception, message) #:nodoc:
           case @connection.error_code(exception)
           when 1
             RecordNotUnique.new(message)
+          when 60
+            Deadlocked.new(message)
           when 900, 904, 942, 955, 1418, 2289, 17008
             ActiveRecord::StatementInvalid.new(message)
           when 1400

spec/active_record/connection_adapters/oracle_enhanced_adapter_spec.rb

@@ -561,4 +561,50 @@ class ::TestPost < ActiveRecord::Base
 
   end
 
+  describe "Transaction" do
+    before(:all) do
+      schema_define do
+        create_table :test_posts do |t|
+          t.string :title
+        end
+      end
+      class ::TestPost < ActiveRecord::Base
+      end
+    end
+
+    it "Raises Deadlocked when a deadlock is encountered" do
+      expect {
+        barrier = Concurrent::CyclicBarrier.new(2)
+
+        t1 = TestPost.create(title: "one")
+        t2 = TestPost.create(title: "two")
+
+        thread = Thread.new do
+          TestPost.transaction do
+            t1.lock!
+            barrier.wait
+            t2.update_attributes(title: "one")
+          end
+        end
+
+        begin
+          TestPost.transaction do
+            t2.lock!
+            barrier.wait
+            t1.update_attributes(title: "two")
+          end
+        ensure
+          thread.join
+        end
+      }.to raise_error(ActiveRecord::Deadlocked)
+    end
+  end
+
+  after(:all) do
+    schema_define do
+      drop_table :test_posts
+    end
+    Object.send(:remove_const, "TestPost") rescue nil
+    ActiveRecord::Base.clear_cache!
+  end
 end