on ConcurrentHashMap, containsKey is faster than contains, since contains() is a synonym for containsValue, and will iterate over the whole map

Fix bug in MVStore when creating lots of temporary tables, where we could run out of transaction IDs.    

Concurrent CREATE TABLE... IF NOT EXISTS in the presence of MULTI_THREAD=TRUE could throw an exception.

so that it was effectly 1024 times smaller than it should be.

MVStore: updates that affected many rows were were slow in some cases if there was a secondary index.

Using "runscript" with autocommit disabled could result in a lock timeout on the internal table "SYS".

When using the MVStore, running a SQL script generate by the Recover tool from a PageStore file failed with a strange error message (NPE), now a clear error message is shown.

Issue 603: there was a memory leak when using H2 in a web application. Apache Tomcat logged an error message: "The web application ... created a ThreadLocal with key of type [org.h2.util.DateTimeUtils$1]".

Issue 605: with version 1.4.186, opening a database could result in an endless loop in LobStorageMap.init.