For testing purposes and not only, it may be needed to evaluate an arbitrary SQL expression (see https://github.com/doctrine/dbal/pull/3013, https://github.com/doctrine/dbal/pull/3108). Instead of doing `str_replace()` on an expected string, one could specify the expression explicitly.

The SQLite and Oracle platforms produces a `ROUND()`'ed or `TRUNC()`'ated difference between the datetimes. However it should be the difference between dates.

Fix PSR2 rules : "As per PSR2, the static declaration should come after the visibility declaration."

 Closes #2436

fixes #2270

Fixed inconsistent use of getSQLDeclaration method

This reverts commit 5a46f577.