new signal extensions

[Tero Pulkkinen <terop modeemi cs tut fi>]

Okay, I've made some new signal extensions -- It seems to work ok and
the code is kinda simple. (I dumped the idea of giving gtk any
information on signals happening in C++ world - it made it very simple
and straightforward implementation..) Take a look at it... 
Get gtk---0.3ext2.tar.gz from http://www.iki.fi/terop/sigslot.html and
tell me if you like it...

(oh, there are other changes in that too.. fixed few typos from the
phil's implementation of the #define hack. Also added border_width(gint)
function to Gtk_Container. Then made some runtime checks to test if
parameters given as GtkAdjustment* are NULL or not -- it seems that
its common that those are given as NULL in plain gtk, I thought it'd
be good to have that option in C++ too..)

But... before new release of gtk--, I should make some stuffs ready:
 * cbdata (so that can give data at connect() call and it'll pass those
   to the slot when signal is called (but we should have this too typesafe,
   not gpointer!)
 * #define hack for the new signal stuffs -- I didnt do this yet because
   of cbdata will be easier to do without it.

-- Tero Pulkkinen -- terop@modeemi.cs.tut.fi --