Bug 7003: jam: Improve API and test specifications

* sources/lib/jam/jam-ir.dylan
  (<jam-arg>): Define as including <string> rather than <byte-string>.

* sources/lib/jam/jam-state.dylan
  (jam-variable, jam-variable-setter): Allow variable names to be general
   instances of <string>.
  (jam-rule, jam-rule-setter): Allow rule names to be general
   instances of <string>.

* sources/lib/jam/jam-evaluator.dylan
  (jam-invoke-rule): Allow rule names to be general instances of <string>.

* sources/lib/jam/jam-reader.dylan
  (jam-read): Allow the input to be a general instance of <string>.

* sources/lib/jam/tests/jam-test.dylan
  (module-spec jam): Do not use unexported types in the defined
   signature of jam-target-bind.
Update splash screen copyright date to 2014
[Testing] Comment out assertion for division by zero that crashes test suite on C back-end.
[Testing] Remove forward references from test suites to adjust to changes in Testworks commit a88a14efb9ba9696d9936cfbbd6649c495eeb45a
[doc] Add a release note about Testworks compiler warnings and forward refs.
[Testing] Output library-spec after module-specs in test-suite report.
[doc] Remove some depth from the release notes toc tree.