This reverts commit ae6da320, reversing
changes made to 8b018f2b.

This reverts commit a45edd78.

and add  a another test case for datediff

by using reader-writer lock, reported issue #538

While we currently support TIMESTAMP WITH TIME ZONE and OffsetDateTime
the corresponding JDBC type TIMESTAMP_WITH_TIMEZONE(2014) is not
supported when calling PreparedStatement.setObject(int, Object, int).

When using CHAR(N) in PostgreSQL any inserted value smaller than N
characters will be right-padded with spaces to fill all N characters.
See: https://www.postgresql.org/docs/9.1/static/datatype-character.html

This change adds an additional Mode.padFixedStrings and set it to true
in the PostgreSQL Mode. Any value converted to a ValueStringFixed at
INSERT will be right-padded with spaces.

For additional infos see the H2 Google Groups post:
https://groups.google.com/forum/#!topic/h2-database/Luaxdrl137Y