More NEWS updates.

NEWS.md

@@ -24,6 +24,10 @@
 
  - Use openssl's `-verify_hostname` option in the rsync-ssl script.
 
+ - Optimize the AVX2 checksum code a bit more.
+
+ - Some manpage improvements.
+
 ### PACKAGING RELATED:
 
  - When creating a package from a non-release version (w/o a git checkout), the
@@ -36,6 +40,11 @@
 
  - Added a SECURITY.md file.
 
+### DEVELOPER RELATED:
+
+ - Made it easier to write rsync tests that diff the output while also checking
+   the status code, and used the idiom to improve the existing tests.
+
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