More expressive sync modes

[arj4web]

loop{
        if((*full == 1'b0)&&(*head == *tail)){
            send ep.empty(1'b1)
        }
        else{
            send ep.empty(1'b0)
        } >> 
        cycle 1
  }

Static sync mode mismatch between ep@empty and ep@empty (actual gap = 1048576 > expected gap 1)!
fifo.anvil:70:12:
     70|             send ep.empty(1'b1)
       |             ^^^^^^^^^^^^^^^^^^^

There are other ways to express but can be convenient enhancement

[arj4web]

We can have generalised sync modes that say a process is ready to receive anytime after an event i.e a message exchange:

For example :

chan foo{
    left req : (logic@#1),
    right res : (logic@#1) @dyn - @#req
}

This basically says the right ep is ready to recv anytime after req