compiler/module_imports.m:
Don't just scan a few kinds of items, scan all items that contain
goals and/or terms. This includes the instance items that caused
mantis bug 371, as well as some others (promises, mutables, and
type definitions).
compiler/prog_data.m:
Delete an out-of-date comment.
tests/valid/string_format_in_instance.m:
Add the Mantis test case under a meaningful name.
tests/valid/Mmakefile:
Enable the new test case.
