RFC version issues

[Ross McFarland <rwmcfa1 neces com>]

there's a bunch of issues that revolve around the fact that the bindings
are compiled against a particular version of gtk+ and only have the
functions associated with that version. basically it comes down to the
fact that you can't trust the information that comes out of
check_version and get_version_info b/c their info comes form the
dynamically linked libraries. 

here's the scenario:
      * system starts with gtk+ 2.0.6
      * you dl and install Gtk2 1.023 
      * you now have bindings for the things in gtk+ 2.0.6,
        check_version and get_version info will be correct and will tell
        you what's available to you)
      * up upgrade gtk+ to 2.4.2 when it comes out
      * now check_version and get_version_info tell you you've got gtk+
        2.4.2, but the bindings were compiled against 2.0.6 so they only
        have the wrappers for stuff available in it.

this is problem because there's no way for an app to tell what it has
available to it. the two possible solutions are:

1) modify check_version and get_version_info to return the compiled
against stuff which would tell you what you have available.

don't like this b/c it changes the documented behavior of existing gtk
functions.

2) add two new functions, for example check_bound_version and
get_bound_version_info. these would return the versions Gtk2 was
compiled against and therefore what is available to the app.

optionally warning messages could be printed saying not to use
check_version and get_version_info b/c they're almost useless. (they
could be useful if you're trying to work around bugs in gtk+ so this
probably isn't a good idea)

a separate issue is the case where bindings were compiled against a
newer version then they are now being linked against. this is a big
problem that could result in undefined symbols. i propose that a warning
message be printed out when this situation is encountered. it is not
necessarily fatal, but could be a source of many problems.

the implementation of #2 and the separate issue:
http://www.neces.com/gtk2-perl/gtk-xs_versions.patch

an patch that can be applied, includes ^:
http://www.neces.com/gtk2-perl/versions.patch

a big question is what should the 2 new function be called to make it
clear.

discuss away.
-rm