[gnome-db] GValue and GdaValue implementation

[Daniel Espinosa <esodan gmail com>]

As we know, the implementation of Gda# in Mono is stoped becouse a bug
in GdaValue, and the reason is that the code parser of gtk-sharp don't
parse Unions (may becouse unions don't exist in C#).

Then, to make GdaValue work in Mono, and may be work better in other
languages, I began to work in a implementation of GdaValue using
GValue as a container.

In the work I find that you need that a value stored in GValue, must
have a GTypeInfo, and for a fundamental types (not objects, as far I
know), you need GTypeValueTable, in  order to be handle correctly by
GValue functions.

For types like GdaTime, GdaDate and so on, I derived this ones from
GObject, then the GValue works well (I tested it).

For types like gint64, gchar and other with a G_TYPE_* associated, the
GValue works well, but this one are fundamental types (as far I know,
not too easy to implement in the GType system), but this is no problem
becouse have a valid GType and can be handle by GValue's functions.

But there exist types like: gshort, gushort, gchar (as tinyshort) and
guchar (as tinyushort), that don't have a G_TYPE_* value associated,
the must need implemented. Becouse this is not a easy work, I want to
know if this types of values, is stricted used by the API and
providers, if so to begean to work in implementing as GType valid
implementation in order to use GValue.