SQLite3 3.6.8+ supports savepoints

http://www.sqlite.org/lang_savepoint.html
https://github.com/rails/rails/blob/master/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb#L130-L132
Merge pull request #9605 from neerajdotname/sqlite-support-savepoint

SQLite3 3.6.8+ supports savepoints