[Truffle] Implement {Module,Class}#initialize and {class,module}_exec.

* Unnamed modules should not have a lexical parent.
[Truffle] Be safer in MRIBacktraceFormatter with NullSourceSection.
[Truffle] Ensure a RubyMethod has the right declaringModule.
[Truffle] Extract a few helper methods in method definition nodes.
[Truffle] Anonynous classes should have unset parent so the singleton class has the right parent.
[Truffle] Add ModuleOperations.lookupSuperMethod.

* And try to partially fix AbstractGeneralSuperCallNode.
update testing commands
uniform setting path to jruby home - no detection just use the one from the classloader
warn when jruby home is not set to one of the tested cases
add null check and change error type
[Truffle] Implement Regexp#initialize_copy.
[Truffle] Implement Regexp.new(regexp).

* Copy and recompile to be sure to have no dependency for now.
[Truffle] A couple passing specs.
[Truffle] Fix index of rest arguments.
Merge pull request #2191 from tduehr/test_doc

update testing commands
Merge pull request #2192 from k77ch7/GH-2050_on_master

Fix for issue 2050 on master: BigDecimal and nil multiplication
[Truffle] Move frozen status to BasicObject.

* We can use methods of Kernel and bind them on BasicObject:

> f = Kernel.instance_method :freeze
=> #<UnboundMethod: Kernel#freeze>
> b=BasicObject.new
=> #<BasicObject:0x62e2d8>
> is=Kernel.instance_method :frozen?
=> #<UnboundMethod: Kernel#frozen?>
> is.bind(b).call
=> false
> f.bind(b).call
=> #<BasicObject:0x47ef28>
> is.bind(b).call
=> true
[Truffle] Make RubyBasicObject.freeze private and propagate to singleton class.

* Fix bad formatting in frozenError().
[Truffle] Defining a method returns a symbol of the method name.
[Truffle] String#length is an alias of String#size.