Link -lrt only on platforms which have the library
Support json-c on Arch Linux
Merge commit '282cc561fc0676abd1d57f1bd5a480aa3154a753' into releases/1.4

* commit '282cc561fc0676abd1d57f1bd5a480aa3154a753':
  Support json-c on Arch Linux
  Link -lrt only on platforms which have the library
Set version numbers for 1.4.3 release
Include m_changes in key_state "finished" method
Fix a race condition in state_hash_table.

An iterator could lock the latest item stored under a given key, but return
pointer to a previous state stored under the same key.  Would lead updates to
appear "lost" and not retransmitted.
Finish implementing prev commit.

Messed up add -p
Execute multiple transfers in parallel
Merge branch 'master' into releases/1.4

* master:
  Execute multiple transfers in parallel
  Finish implementing prev commit.
  Fix a race condition in state_hash_table.
  Include m_changes in key_state "finished" method
Set version numbers for 1.4.4 release