ruby: make sure that we interpret all metadata as UTF-8
ruby: fix source code line for struct/class/enum

GCCXML reports the line of the opening bracket ({) while we really
would like the definition line (struct/class/enum)
ruby: small style fix, remove duplicate call to resolve_type_id
ruby: test for proper parsing of files containing utf-8 characters
ruby: define Registry#add
improve some error messages
in minimal(), do not auto-build useless derivative types
test: fix the IDL export tests
ruby: fix comparison of Typelib::Type with a class that is a direct subclass of Object

The "technique" used to so far to determine in Type.== whether we should
go on with the comparison fails if we were comparing Typelib::Type with
e.g.  Class.new. The reason was that we were looking at the superclass,
which is a bad idea in this case (the superclass in both cases is Object)
ruby: fix #pretty_print on root classes
ruby: fix comparison of type with a base type class

This should be the last one. Base classes now have an initialization
step that allows to make them really look like the actual types.
We use this to set a proper @type instance variable that == can
access and use for comparison