SubT Virtual: optimize multiple explorations

[m3d]

The robot can explore the world multiple times, for example code A10F200F450L means wait 10s, explore for 200s, return to the base and then explore again 450s along the left wall. In the second exploration it will "waste" repeating long way even in to dead-ends. It would be smarter to re-use turn path from the first exploration. Note, that the code is already there (see follow_trace()).