somebody reported an error, and they think the PageStore#changeCount field has wrapped and become negative.
Put a check in place to make such a situation more obvious.

git-svn-id: http://h2database.googlecode.com/svn/trunk@4885 e6896862-9d19-0410-bfb3-e9fa5d50e656
change the PageStore#changeCount field from an int to a long, to cope with databases with very high transaction rates.


git-svn-id: http://h2database.googlecode.com/svn/trunk@4886 e6896862-9d19-0410-bfb3-e9fa5d50e656