Update CHANGELOG (actually, mostly done in last commit by mistake).

git-svn-id: https://www.prismmodelchecker.org/svn/prism/prism/trunk@3264 bbc10eb1-c90d-0410-af57-cb519fbb1720

prism/CHANGELOG.txt

@@ -3,7 +3,7 @@ including development and beta versions. For a less detailed overview
 of the main changes in each public release, see the file VERSIONS.txt.
 
 Latest changes (mostly reverse chronological):
-[correct wrt svn rev 3250]
+[correct wrt svn rev 3263]
 
 * Added if-and-only-if operator (<=>) for use in models/properties
 * Properties can be named, by prefixing with "name":, and reference each other
@@ -11,10 +11,10 @@ Latest changes (mostly reverse chronological):
 * Testing mode (-test and -testall switches)
 * Various bug fixes
 
-* CTL AG/EF
-
 Ongoing changes:
 
+* More improvements to explicit engine
+* CTL AG/EF
 
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 Version 4.0 (released 28/6/2011)