shared idl types

[Dave Camp <dave ximian com>]

I'm looking at gnome-debug and gnome-build, and I think we should push a
few of the idl types in GNOME::Development to gdl and let the modules
share them.

In particular, both modules deal with source files.  gnome-debug just
uses a uri, while gnome-build uses a struct that contains a uri.  We
should decide on one way of doing it (my vote is for just using a uri),
and move Source and SourceList (sequence of sources) into gdl.

source/line number information is also a common type.  We should have a
SourceLocation struct (with source and line number fields).  gnome-debug
will use this for current line information, gnome-build would use it in
the BuildError struct.

If nobody objects I'll move the Source (typedef string), SourceList
(sequence of source), and SourceLocation (struct { Source source; long
line_num; }) types from gnome-debug into gdl when the gnome2 port of gdl
is ready.

-dave