Add the first NEWS entry for 1.2.3

This commit was SVN r14696.

NEWS

@@ -52,6 +52,13 @@ Trunk (not on release branches yet)
   --> Expected: 1.3
 
 
+1.2.3
+-----
+
+- Fix the mvapi BTL to compile properly with compilers that do not support
+  anonymous unions.  Thanks to Luis Kornblueh for reporting the bug.
+
+
 1.2.2
 -----