EXISTS / NOT EXISTS clause support for  DB_query_builder.
EXISTS / NOT EXISTS clause support for  DB_driver
EXISTS / NOT EXISTS clause support for  DB_driver
changed EXISTS / NOT EXISTS pattern
@narfbg "It has parenthesis, so use the IN / NOT IN pattern as a base."
added changelog about EXISTS / NOT EXISTS
@narfbg "And you should also add a changelog entry for this addition. :)"
so we need \sNOT EXISTS
Merge pull request #2781 from tufanbarisyildirim/develop

EXISTS / NOT EXISTS clause support for  DB_driver