Deprecating gtk_signal_* gtk_object_*

[Owen Taylor <otaylor redhat com>]

Based on comments in the documentation, #61942 calls for
for marking virtually all of gtkobject.h GTK_DISABLE_DEPRECATED.
(Except for gtk_object_sink(, gtk_object_destroy())

If we do that, we should presumably correspondingly deprecate
all of gtksignal.h.

 - Pro: People would be better off not using this stuff in
   new code, and deprecating it hopefully will hopefully
   provide protection against people using it in example
   code.

 - Con: Making code GTK_DISABLE_DEPRECATED clean becomes
   even more of a pain and people may just not bother.

In balance, I think I favor doing this, but I'd like
other opinions.

Thanks,
                                        Owen