Expressed PARAM_*_ARRAY through other constants to eliminate the dependency on the actual constant values

Close #2998
the commit.

Simplify returns

Update license's copyright

Fix annotation types

[DBAL-2954] Removed error suppression in IBM DB2 Statement

Implemented Statement::fetch(PDO::FETCH_COLUMN) in non-PDO driveres

Fixes #2953.

Update Doctrine CS requirement

Use Null Coalesce Operator

This reverts commit e3ab1276, reversing
changes made to f988b0a6.

Fixed code style check failures for pull request against non-master branches

Fixes #2961.

Support for backslashes in default values

Whitespaces clean-up in docs