Simulated Aseba targets have unexpected event execution policies

Created by: stephanemagnenat

Simulated Aseba targets do not behave like real targets with respect to execution policy:

• After commit 65b15c56, asebadummy executes 1000 VM steps for every received events and 50 Hz timer.
• asebaplayground and asebachallenge and execute 1000 VM steps for periodic events and for the last received event fromHub::step(), but will kill any previously received during that step.
• asebamarxbot will execute the last received event from a Hub::step() for 65536 VM steps, and kill any previously received. An event received from a Hub::step() will kill the periodic event if it happens just after.