Removes deubugging printouts.

That’s all.
Adds new tests and improves test harness.

Add tests for type features.
Abbreviates test harness output for passing tests.
Parses and generates code for type expressions.

Adds new AST nodes typedef and typeliteral.  Type expressions
are represented as expression trees, which are evaluated at runtime
using the usual mechanism for expressions — method request.

Type operators &, | - and + are now defined in the StandardPrelude.
In the JS code, this necessitates that the methods in the
StandardPrelude are _added_ to Grace_prelude incrementally,
rather than when the import is completed.   Thus, StandardPrelude
is now imported specially in JS. _prelude is no longer inherited.
This simplifies the setup in the web browser and in the node.js test
harness. Adds new methods to gracelib.js to support types, and
removes dead code.

These changes have been incorporated into the C backend only as
far as necessary to support the new parse tree structure.  Features
not used by the compiler are not included in the C code generator,
nor in gracelib.c
Removes catch from do_import.

This just confused the output when there was an error.
Changes default visibility for JS tests.

Several tests failed without DefaultVisibility=public,
and were modified to give the approriate access to fields.
Also, the two test harnesses were made uniform.
Output from the tests was neatened, and summary
information added to the log file, which now records just failures.
Cleans up type declarations.

This completes th type declarations changes.
ast module — last remnants of type node removed.
    adds some methods to cleanly get the declared name
    (as a String) from declaration nodes.
genc module — removed dead variable, tried (but failed) to
    add accessor method for name introduced by import … as
genus module — add accessor for name introduced by import,
    and small optimization for methods that are simple accessors.
    removes last vestiges of typenodes.
gracelib.h — removes 2 (!) declarations of ProgrammingError()
    this was introduce by me in unnecessarily in d8a383f2
identifierResolution — add decls of built-ins, removes dead code.
    tries to import StandardPrelude names in the same way as other
    modules, but eventually falls back to old code.
StandardPrelude — adds comments, changes annotation to public