Fix a number of issues in the new one sided code.

 - Fix several typos is osc/rdma.

 - Fix a locking issue in osc/sm that was caused by an incorrect
   assumption about the semantics of opal_atomic_add_32.

 - Always unlock the accumulation lock in osc/sm.

 - The base of a processes shared memory window should be NULL if
   the size is zero. Fixed.

cmr=v1.7.5:ticket=#4304
udcm: fix race between ack arrival and message send and potential hang in udcm
finalize.

Closes #4290

cmr=v1.7.5:reviewer=miked