update appraisal:rails40 to 4.0.0.rc1 (from 4-0-0-stable)
quote_table_name_for_assignment should only be added on AR >= 4.0
quote_table_name_for_assignment for MS-SQL 

+ #current_user and #default_schema might be needed during an API (exec) method thus should not use the connection API while querying the database
on MS-SQL repair columns from exec_query_raw as well & use super impl +
4.0 compatibility due missing quote_value and deprecated inst.connection
SQLServer visitor compat with next AREL

also there's a failure and an error (against AR 3.2):
- Failure: test_limit_with_group_by(MSSQLLimitOffsetTest)
- Error: test_limit_with_no_id_column_available(MSSQLLimitOffsetTest)

not sure when these started happening ... last MS-SQL PR seems unrelated
some 4.0 test compat (TableDefinition#xml no longer available for all)
+ add decimal with scale for chasing down a PG failure from Rails suite