Partial changes to do with Eiffel 7.3 upgrade:

- uses latest gobo git rather than ISE gobo libs and tools
- uses detachable types in parsers as initially required by 7.3 compiler, but these might be abandoned (see list).
Update old comments.
Void-safety changes for compilation under Eiffel 7.3. Uses gobo latest Git, not ISE_EIFFEL libs.
Fix void-safe referencing code.
Adjust .ecf files so that $GOBO-based ones that work for Eiffel 7.3 are now the standard ones.