Add support for filtered indexes for mssql dialect
Added support for SQL Server filtered indexes, via the ``mssql_where``
parameter which works similarly to that of the ``postgresql_where`` index
function in the PostgreSQL dialect.
Fixes: #4657
Closes: #4658
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/4658
Pull-request-sha:
cf609c19bccc74c0dba38d2fc4976df3a205f3f6
Change-Id: I9c61b97d0b0cb6f6d417da7b1875b40f8f918a3c
(cherry picked from commit
174f2ae33b5235d709b17f3371946a173defaa0d)