MS SQL Srv

Hey,
i have worked on the sqlsrv implementation a bit : https://github.com/puschie286/CodeIgnite.../mssql-srv

its a very rough implementation, many functions are simply copied and adjusted to implement limits at the query beginning.

there are still a few problems that are not handled automatically:
* update, insert that contain index value data (identity column data)
* cast to int for text/varchar increment/decrement

im not sure how to implement the identity detection in a way that result not in an additional request on every update/insert