Import GtkTreeView from GTK+ 2.0-2.20.1 renamed as PsppSheetView.

Import GtkTreeView from GTK+ 2.0-2.20.1 renamed as PsppSheetView.

This includes minimal modifications to make it compile and link
cleanly.

I used the following Perl script to do the bulk of the renaming:

for $pair (['tree_view_column', 'sheet_view_column'],
           ['tree_selection', 'sheet_selection'],
           ['tree_view', 'sheet_view'],
           ['rbtree', 'rbtree'],
           ['rbnode', 'rbnode']) {
    my ($from, $to) = @$pair;

    my ($tfrom) = join ('', map ("\u$_", split ('_', $from)));
    my ($tto) = join ('', map ("\u$_", split ('_', $to)));

    s/gtk_$from/pspp_$to/g;
    s/\Ugtk_$from/\Upspp_$to/g;
    s/GTK_TYPE_\U$from/PSPP_TYPE_\U$to/g;
    s/GTK_IS_\U$from/PSPP_IS_\U$to/g;
    s/Gtk$tfrom/Pspp$tto/g;
}

s/GtkTreeCellDataFunc/PsppSheetCellDataFunc/g;
s/GtkTreeDestroyCountFunc/PsppSheetDestroyCountFunc/g;