[Checkers] Changelog entries for Checker Framework

[Michael Ernst]

Telmo-

You wrote good changelog entries about implementation changes in the Javari
checker, which were informative and useful to me.  Thanks!  However, they
are probably not interesting to the audience who will be reading the
changelog -- few people are following its implementation so closely.

However, changelog-checkers.txt should focus on user-visible changes.
(Those users could be either checker users -- programmers -- or framework
users -- type system designers.)  In general, don't mention changes with no
user-visible behavior.  If a change has user-visible behavior, then
describe it with respect to what bug got fixed or how the behavior changes
-- not how the implementation changed.

I removed the changelog entries for the Javari checker implementation.
However, feel free to re-add these things as appropriate.  The changelog
entry may list any change that hasn't yet been mentioned in the changelog
-- even if the change was made in a previous release.  (An undocumented
change is a change that doesn't exist!)

                     Thanks,

                    -Mike