[mpi3-coll] Simplify "local completion" to just "completion"

[Adam Moody]

I think we could reduce "local completion" to just "completion" 
throughout the text.  I don't think the adjective "local" is necessary 
and in some ways I find it confusing.  We define precisely what 
"completion" means in a collective, and we also explicitly note that 
completion at a process does not indicate the status of other 
processes.  Whenever we say "local completion", we really mean 
"completion" by our definition, so "local" is not necessary here.  And 
by saying "local" completion, it sounds as a reader that there may be 
such a thing as "non-local" completion, but we don't define it.  There 
is only one definition for collective completion.
-Adam

p 2, line 17 in "Collective operations can (but are not required to) 
complete locally as soon as the caller's participation in the collective 
communication is finished."
    "complete locally"  -->  "complete"

p 2, line 20 in "The local completion of a collective operation 
indicates that the caller is free to access locations in the 
communication buffer."
    "The local completion" --> "The completion"

p 49, line 48 & p 50, line 1 in "Once initiated, all associated send 
buffers should not be modified and all associated receive buffers should 
not be accessed until the collective operation completes locally."
    "until the collective operation completes locally." --> "until the 
collective operation completes."

p 51, line 32 in "On intracommunicators, the operation completes locally 
after every process in the communicator called MPI_IBARRIER."
    "the operation completes locally" --> "the operation completes"
and (to preserve verb tense)
    "after every process in the communicator called"  -->  "after every 
process in the communicator calls"