Refactor how code unit information is passed from PHPUnit

[sebastianbergmann]

PHPUnit turns code unit information (@covers class::method, for instance) into filename and line numbers information which this component then uses but has to convert back into code unit information when, for instance, a CoveredCodeNotExecutedException has to be raised.

It would be better for PHPUnit to pass lists of code units (from @covers and @uses annotations) to this component instead.