Implemented interprocess shared memory RMA ops

Communication operations on shared memory windows now perform the op directly
on the shared buffer.  This requried the addition of a per-window interprocess
mutex to ensure that atomics and accumulates are performed atomically.

Reviewer: buntinas
Sock implementation of interprocess shm mutex

The sock implementation of the per-window interprocess shared memory mutex is
currently a no-op, because shared memory windows are not supported in sock.

Reviewer: buntinas
Shr. Mem. RMA: Flush is now a nop

Reviewer: buntinas
RMA test case: MCS mutex lock/unlock

A new test case that uses the Mellor-Crummey and Scott mutual exclusion
algorithm.

Reviewer: buntinas
Updated MCS mutex test to also use shr. mem win.

Updated the MCS mutex test to work with both regular and shared memory windows.

Reviewer: buntinas
autogen.sh: use `cp -pPR` instead of `cp -a`

On niagara1, `cp -a` does not work.  But the equivalent `cp -pPR` does.

No reviewer.
Fixed error checks in shr. mem. win. creation

Replaced SETANDJUMP with CHKANDJUMP, so we actually check for a pthread error
before signalling an MPI error.

Reviewer: none