Implement better checking of extends in new instantiation

[Per Östlund]

Extends are currently fully qualified in the new instantiation, since they may not be redeclared. We should do this in a better way so that we can detect if any part of the path is replaceable. We should also check the restriction that extended classes shouldn't be found in any of the extends in the scope while doing the qualifying, so we can avoid doing that the rest of the time and simplify the lookup.

[Dietmar Winkler]

It doesn't make sense to keep closed ticket in the "Future" milestone that were simply forgotten to assign to the correct milestone in the past.

[Martin Sjölund]

Removing the pre1.9.4 milestone in favor of 1.9.4.