Add -Yno-load-impl-class disabling loading of $class.class files.

The parent commit, a3f71badf67bbaac1a4ba16f68211ea6e31aa473,
removed some logic preventing $class.class files to be
loaded. It did so only when the inliner was off.

Should this cause any issue, this option provides a means to
restore the old behavior by *never* loading $class.class files.

So, using -inline -Yno-load-impl-class will not load
$class.class files either (where previously -inline would
load them). The two old behaviors being available by *either*
using -inline *or* -Yno-load-impl-class (not both).