Type and name sql argument of query function

[rey0bs]

Several functions use first argument of Connection::query function. This argument is named and typed as string in functions which use it, but is not documented in query function.

For example, in Doctrine\DBAL\Connection, the logger uses it in startQuery function. $sql is named and typed in SQLLogger interface, but not in query function.

This PR names this argument to increase visibility and avoid to use func_get_args and $args[0] for $sql parameter.

[Majkl578]

This change is a BC break and couldn't be considered for 2.x.

[morozov]

Obsolete as of #3803.