Use relative names in inline {@link} annotations where possible

Update Slevomat Coding Standard to 6.3.10

Update PHPStan to 0.12.31

Update PHPStan to 0.12.30

Bump Psalm level to 5

Fix handling host and port configuration in sqlsrv and pdo_sqlsrv drivers

Fix DSN detection in the IBM DB2 driver

Simplify test suite configuration

Report coverage unconditionally on Travis

pcov is fast enough for this to be acceptable.

Integrate with Codecov

@link in convertException gives 404