Replace global clock with Lamport timestamps

[lou1306]

1. In the header, replace int __LABS_t with an array unsigned int clock[MAXCOMPONENTS]. Change the now() function so that it takes the agent's id as an argument.
2. Inside init(), increase clock[0] when initializing stigmergic variables. At the end, set all elements of clock to the value of clock[0].
3. Change confirm and propagate with a tie-breaking rule.

Feasible tie-breaking rules

Agent with lowest id "wins"

✅ original solution from Lamport,
✅ also the one used in Buzz
❌ requires to keep track of the id with another array Lid[MAXCOMPONENTS][MAXKEYL]

Smaller or equal Lvalue wins

✅ No changes to the data structures
❌ Requires some theoretical justification (eg. will the stigmergy be stable?)