Fork Consistency

Server orders events sequentially (correct server).

updating (events):

c1: -<c1_u1>----------------------------------<c1_u2>-----------------------------------

c2: ---------------------<c2_u1>--------------------------------------<c2_u2>-----------

ordering:

s:   (c1_u1)             (c2_u1)              (c1_u2)                 (c2_u2)

c1:  (c1_u1)             (c2_u1)              (c1_u2)                 (c2_u2)
c2:  (c1_u1)             (c2_u1)              (c1_u2)                 (c2_u2)