API change summaries and fixes to the code. Doc correctsions 
and/or changes are not mentioned here; see the commit messages.

2019 July 15; Version 1.0.39
	Prevent unnecessary usleep in retry loop.

2019 July 12; Version 1.0.38
	Added new message types to RIC_message_types.h.

2019 July 11; Version 1.0.37

	librmr and librmr_nng 
		- Add message buffer API function rmr_trace_ref()
		  (see rmr_trace_ref.3 manual page in dev package).