boxed types and copies

[Havoc Pennington <hp redhat com>]

Hi,

The recent gtk_signal_emit() change broke the text widget - I'm using
GTK_TYPE_TEXT_ITER, GTK_TYPE_STRING, etc. for the signal signature, 
at James' request, so Python can emit these signals.

However these signal args MUST be passed by reference, it is far too
slow to copy the inserted string, and the iterator is supposed to be
modified by the signal handlers.

Moving gtk_signal_emit() to the GValue collector causes it to
copy-by-value every boxed argument. So I either have to move back to
GTK_TYPE_POINTER and break language bindings, or leave GtkTextBuffer
broken.

Havoc