Add debug informations for the compiled methods

Debug informations store the argument name and temporary variable
names in a dictionary. And add some methods to retrieve them.
Add debug information support in the Smalltalk compiler
Add a new Kernel-Tests package and a better support for method copying.

When a compiled method is copied some literals (block and closures)
need to be updated: they have references to the old method. The debug
information also need to be updated to point to the new literals array.