Add CHANGES and release note for [GL #3840]

CHANGES

@@ -1,3 +1,9 @@
+6094.	[bug]		Building against (or running with) libuv versions
+			1.35.0 and 1.36.0 is now a fatal error.  The rules for
+			mixing and matching compile-time and run-time libuv
+			versions have been tightened for libuv versions between
+			1.35.0 and 1.40.0. [GL #3840]
+
 6093.	[performance]	Reduce the size of each rdataset header object
 			by 16 bytes. [GL !7505]
 

doc/notes/notes-current.rst

@@ -32,7 +32,26 @@ Removed Features
 Feature Changes
 ~~~~~~~~~~~~~~~
 
-- None.
+- libuv support for receiving multiple UDP messages in a single system
+  call (``recvmmsg()``) has been tweaked several times between libuv
+  versions 1.35.0 and 1.40.0; the recommended libuv version is 1.40.0 or
+  higher. New rules are now in effect for running with a different
+  version of libuv than the one used at compilation time. These rules
+  may trigger a fatal error at startup:
+
+  - Building against or running with libuv versions 1.35.0 and 1.36.0 is
+    now a fatal error.
+
+  - Running with libuv version higher than 1.34.2 is now a fatal error
+    when :iscman:`named` is built against libuv version 1.34.2 or lower.
+
+  - Running with libuv version higher than 1.39.0 is now a fatal error
+    when :iscman:`named` is built against libuv version 1.37.0, 1.38.0,
+    1.38.1, or 1.39.0.
+
+  This prevents the use of libuv versions that may trigger an assertion
+  failure when receiving multiple UDP messages in a single system call.
+  :gl:`#3840`
 
 Bug Fixes
 ~~~~~~~~~