API and build change and fixe summaries. Doc correctsions
and/or changes are not mentioned here; see the commit messages.
+2019 August 26; version 1.4.0
+ New message types were added.
+
+2019 August 16; version 1.3.0
+ New mesage types added.
+
+2019 August 13; version 1.2.0 (API change, non-breaking)
+ The function rmr_get_xact() was added to proide a convenient
+ way to extract the transaction field from a message.
+
2019 August 8; version 1.1.0 (API change)
This change should be backward compatable/non-breaking
A new field has been added to the message buffer (rmr_mbuf_t).