add circa_set_log_handler
support log handler in print() and dumping funcs
add circa_term_get_function
Fix call_to_non_function test
spring cleaning: finally remove import_macros.h
builtins are now all in a top-level module called 'builtins'
Some initial work on modules
Fix name lookup to work properly with modules
remove generate_cpp module
Phasing out the Function type (use Block instead)
add test non_required_module_is_not_visible
unknown_identifier is now a runtime error
Bug fix, now closures work when called as dynamic methods
unrecognized_expression() now throws a runtime error. Not doing so was a poor idea
Minor cleanup in token.cpp
Various fixes around memory leaks. Delete incomplete GC code
delete Function type

- Store functions as Blocks
- Rename Closure to Func
- Function decls work as closures
eliminate obsolete dll_loading.cpp (replaced by native_patch)
Delete obsolete actors.cpp
remove unnecessary evaluate_subroutine