Add support for MySQL's utf8mb4 charset in CREATE TABLE

Server mode: concurrently using the same connection could throw an exception Connection is broken: unexpected status

In DateTimeUtils.getTimeTry(), Calendar instances used to evaluate Timestamps were only being cached if no timezone was specified. I've added code to reuse Calendar instances if the timezone specified matches the previous use.

In DateTimeUtils.getTimeTry(), Calendar instances used to evaluate Timestamps were only being cached if no timezone was specified. I've added code to reuse Calendar instances if the timezone specified matches the previous use.

Server mode: concurrently using the same connection could throw an exception Connection is broken: unexpected status

Server mode: concurrently using the same connection could throw an exception Connection is broken: unexpected status

Multi-threaded processing: concurrent deleting the same row could throw the exception Row not found when trying to delete

MVStore transactions: a thread could see a change of a different thread within a different map. Pull request #153.

MVStore transactions: a thread could see a change of a different thread within a different map. Pull request #153.

Test case for undoLog synchronization race and proposed fix

COLUMNS metatable