Make `LocalJumpError` a subclass of `ScriptError`.

It's incompatible with CRuby, but it is required for mruby because
it cannot detect `break` outside of loops in the parsing time, but
in the code generation time where it cannot raise `SyntaxError`.

mrblib/10error.rb

@@ -2,8 +2,8 @@
 class ArgumentError < StandardError
 end
 
-# ISO 15.2.25
-class LocalJumpError < StandardError
+# ISO 15.2.25 says "LocalJumpError < StandardError"
+class LocalJumpError < ScriptError
 end
 
 # ISO 15.2.26

test/t/superclass.rb

@@ -23,7 +23,8 @@
   [:Exception, :Object, '15.2.22.2'],
   [:StandardError, :Exception, '15.2.23.2'],
   [:ArgumentError, :StandardError, '15.2.24.2'],
-  [:LocalJumpError, :StandardError, '15.2.25.2'],
+  # [:LocalJumpError, :StandardError, '15.2.25.2'],
+  [:LocalJumpError, :ScriptError, '15.2.25.2'], # mruby specific
   [:RangeError, :StandardError, '12.2.26.2'],
   [:RegexpError, :StandardError, '12.2.27.2'],
   [:RuntimeError, :StandardError, '12.2.28.2'],