Update recommended BDB versions.

README

@@ -19,7 +19,9 @@ REQUIRED SOFTWARE
         POSIX REGEX software (required)
 
     SLAPD:
-        BDB and HDB backends require Sleepycat Berkeley DB 4.2 or later
+        BDB and HDB backends require Oracle Berkeley DB 4.2, 4.4,
+        4.5, or 4.6.  It is highly recommended to apply the patches
+        from Oracle for a given release.
 
     CLIENTS/CONTRIB ware:
         Depends on package.  See per package README.