Adding support for the new mssql_n driver

Merged from MOODLE_17_STABLE

lib/setuplib.php

@@ -118,6 +118,7 @@ function setup_is_unicodedb() {
             }
             break;
         case 'mssql':
+        case 'mssql_n':
         case 'odbc_mssql':
         /// MSSQL only runs under UTF8 + the proper ODBTP driver (both for Unix and Win32)
             $unicodedb = true;