common: 2.1.0 documentation update

Signed-off-by: Tomasz Gromadzki <tomasz.gromadzki@intel.com>

ChangeLog

@@ -2,11 +2,24 @@ XXX
 
 	* Version 2.1.0
 
-	This release
-	- introduces fuses against ill-considered use of NDCTL_ENABLE=n
-	  - PMEMOBJ_IGNORE_DIRTY_SHUTDOWN and PMEMOBJ_IGNORE_BAD_BLOCKS are required to acknowledge the understanding of what production-critical functions are missing for the build without NDCTL
-	- does not allow opening pmem pool without unsafe shoutdown counter if not explicitly disabled
-	- remove support for build time define NO_LIBPTHREAD
+	This release :
+	- Introduces the new logging subsystem in the release build for all libraries.
+	  - Messages by default are printed to syslog and stderr but might be redirected to a user defined function,
+	    see pmemobj_log_set_function() for details.
+	  - Log level threshold is cntroled via new API, see pmemobj_log_set_treshold()/pmem_log_set_treshold() for details.
+	  - These new APIs are not available for LIBPMEM2 and LIBPMEMPOOL at the moment.
+	  - The new logging subsystem is suppressed in the debug build when any of the legacy debug logging environment varaible is set:
+	    - PMEM_LOG_LEVEL/_FILE
+	    - PMEM2_LOG_LEVEL/_FILE
+	    - PMEMOBJ_LOG_LEVEL/_FILE
+	    - PMEMPOOL_LOG_LEVEL/_FILE
+	  - The debug logging subsystem becomes DEPRECATED.
+	- Introduces fuses against ill-considered use of NDCTL_ENABLE=n
+	  - PMEMOBJ_IGNORE_DIRTY_SHUTDOWN and PMEMOBJ_IGNORE_BAD_BLOCKS are required to acknowledge
+	    the understanding of what production-critical functions are missing for the build without NDCTL.
+	- Does not allow opening PMEMOBJ pool without unsafe shutdown counter (USC) if not explicitly disabled (#5968)
+	  - use PMEMOBJ_CONF="sds.at_create=0" to disable USC when working without PMem (emulated PMem, Docker, etc.).
+	- Drops support for building without libpthread (NO_LIBPTHREAD build-time define).
 
 Mon Dec 4 2023 Oksana Sałyk <oksana.salyk@intel.com>