Revert "removed MsSqlDriver (is not available with PHP 5.3 or later; replaced with SqlsrvDriver)"

This reverts commit ac1ab26e7a.

tests/databases.sample.ini

@@ -57,6 +57,20 @@ username =
 password =
 system = odbc
 
+[mssql]
+driver = mssql
+host = 127.0.0.1
+username = dibi
+password =
+system = mssql
+
+[mssql pdo]
+driver = pdo
+host = mssql:host=127.0.0.1;dbname=dibi_test
+username = dibi
+password =
+system = mssql
+
 [sqlsrv]
 driver = sqlsrv
 host = (local)