generate error on duplicated data-type accessors. Issue 85

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
fix documnetation to say milli-seconds. Issue 84

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
remove unsound simplification for rem. Codeplex Issue 76

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>