Explicitly unsupported MRI tests

Author: chrisseaton

test/mri/failing.exclude

@@ -1,5 +1,7 @@
-# Explicitly unsupported stdlibs
+# Explicitly unsupported
 
+ruby/test_ast.rb
+ruby/test_jit.rb
 ruby/test_continuation.rb
 dbm/test_dbm.rb
 gdbm/test_gdbm.rb
@@ -169,8 +171,6 @@ matrix/test_matrix.rb # open range
 matrix/test_vector.rb # open range
 ruby/test_arithmetic_sequence.rb # open range
 ruby/test_array.rb # open range
-ruby/test_ast.rb # uses changes to Dir.glob
-ruby/test_jit.rb # obvious
 ruby/test_rand.rb # open range
 ruby/test_range.rb # open range
 ruby/test_rubyoptions.rb # uses RubyVM