Re-introduce bulk_create on supported databases

This fixes etianen#924.

reversion/revisions.py

@@ -1,4 +1,5 @@
 from contextvars import ContextVar
+from django.db import connections
 from collections import namedtuple, defaultdict
 from contextlib import contextmanager
 from functools import wraps
@@ -211,6 +212,7 @@ def add_to_revision(obj, model_db=None):
 
 def _save_revision(versions, user=None, comment="", meta=(), date_created=None, using=None):
     from reversion.models import Revision
+    from reversion.models import Version
     # Only save versions that exist in the database.
     # Use _base_manager so we don't have problems when _default_manager is overriden
     model_db_pks = defaultdict(lambda: defaultdict(set))
@@ -248,9 +250,17 @@ def _save_revision(versions, user=None, comment="", meta=(), date_created=None,
     # Save the revision.
     revision.save(using=using)
     # Save version models.
+
+    can_use_bulk_create = connection[using].features.can_return_rows_from_bulk_insert
+
     for version in versions:
         version.revision = revision
-        version.save(using=using)
+        if not can_use_bulk_create:
+            version.save()
+
+    if can_use_bulk_create:
+        Version.objects.using(using).bulk_create(versions)
+
     # Save the meta information.
     for meta_model, meta_fields in meta:
         meta_model._base_manager.db_manager(using=using).create(