A concurrent queue, to replace the array list of old roots (work in progress)

git-svn-id: http://h2database.googlecode.com/svn/trunk@5781 e6896862-9d19-0410-bfb3-e9fa5d50e656
A tool to clean up full-thread-dump files

git-svn-id: http://h2database.googlecode.com/svn/trunk@5782 e6896862-9d19-0410-bfb3-e9fa5d50e656
rename Database#update to Database#updateMeta for symmetry with the other meta related methods

git-svn-id: http://h2database.googlecode.com/svn/trunk@5783 e6896862-9d19-0410-bfb3-e9fa5d50e656