re-add smartmatch.t to spectest.data

I reviewed and improved it extensively in the last 12H, it should now be on
average much more correct than our average test file.

This commit also removes S12-attributes/class2.t which has been merged into
class.t

t/spectest.data

@@ -8,7 +8,6 @@
 #
 # we've regressed on some files for various reasons:
 # 
-# S03-operators/smartmatch.t - tests themselves are quite wrong in many places
 # S03-operators/binding-arrays.t - regressed to allow slices
 # S03-operators/binding-hashes.t - regressed to allow slices
 # integration/rule-in-class-Str.t - 'is also' -> augment
@@ -138,6 +137,7 @@ S03-operators/reduce-metaop.t
 S03-operators/relational.t
 S03-operators/repeat.t
 S03-operators/scalar-assign.t
+S03-operators/smartmatch.t
 S03-operators/series.t
 S03-operators/short-circuit.t
 S03-operators/spaceship-and-containers.t
@@ -275,7 +275,6 @@ S11-modules/export.t
 S11-modules/import.t
 S11-modules/import-tag.t
 S11-modules/nested.t
-S12-attributes/class2.t
 S12-attributes/class.t
 S12-attributes/clone.t
 S12-attributes/delegation.t