gtkconv and gtkconvwin are in the same file

[Ankit Vani]

Hi

Right now, gtkconv.c contains code intended for gtkconvwin.c as well at the
bottom -- with its own file documentation, copyright header, and includes. This
makes an already long file longer, and also is a little odd.

There are three ways this can go:

1. Do nothing
   Keep things as they are. It has been this way for a while now and works.

2. Split gtkconv.c and gtkconvwin.c
   Perhaps add a header file such as gtkconv-private.h or pidgin-internal.h for
   all the common stuff.

3. Remove the distinction
   Make it all gtkconv. Also move gtkconvwin.h code to gtkconv.h.

What do you guys think?

Ankit