model: end-of-execution print

model: end-of-execution print

For readability of a "verbose" execution log (and even for the shorter,
non-verbose log), it helps to visually separate the final statistics
from any previously-printed statistics. For instance, in the following
verbose snippet from the end of an execution history, it's confusing why
there are two identical copies of the statistics:

... <other execution history> ...
Number of complete, bug-free executions: 4
Number of redundant executions: 0
Number of buggy executions: 0
Number of infeasible executions: 5
Total executions: 9
Total nodes created: 48

Execution 9:
---------------------------------------------------------------------
... <snipped trace info> ...
---------------------------------------------------------------------

Number of complete, bug-free executions: 4
Number of redundant executions: 0
Number of buggy executions: 0
Number of infeasible executions: 5
Total executions: 9
Total nodes created: 48