fix bug in `fast` option: printing temporary terms hid changes in model when...

fix bug in `fast` option: printing temporary terms hid changes in model when the temporary term changed as the temporary terms themselves were not printed. closes dynare#1661

Furthermore, modifications to model local variables were not taken into account.

To fix, take checksum of model local variables, temporary terms, and equations

Also, use existing functions to print these to a stringstream instead of repeating print functionality in this function