new_packet_list_column_button_pressed_cb(): return gboolean (not void): it's an event...

new_packet_list_column_button_pressed_cb(): return gboolean (not void): it's an event callback;
Note:
 the original code:
   static void new_packet_list_column_button_pressed_cb() {
     ...
     packet_list_popup(...);
     }
 the revised code:
   static gboolean new_packet_list_column_button_pressed_cb() {
     ...
     return packet_list_popup(...);
     }

 My guess is that the original code happened to work
 on some?/all? supported platforms depending upon the actual
 details of the generated calling_sequence/return code.
---------------
Also:
- new_packet_list_column_button_pressed_cb(): 'path' arg is unused;
- new_packet_list_double_click_cb(): user_data arg is unused so
  don't supply same in the g_signal_connect.

svn path=/trunk/; revision=33888