* Test the plug-in system in T::R::CL.

* Fix the $Test::Run::Obj::Debug access in Straps.pm.

* $Ignore_Exitcode is assigned once from $ENV{HARNESS_IGNORE_EXITCODE}, but
isn't referenced anywhere else in the code - ask the Test::Harness maintainers
what to do about it.

* Throw objects instead of strings in the _fail functions 
    - otherwise we won't be able to distinguish between regular errors.

* make sure that the string outputted in _report_success(), etc. is 
generated by a method and is not constant.

* Update the documentation - currently it's mostly updated only to 
Test::Harness.

* Eliminate the rest of the unnecessary global variables.
