add two new callbacks:

add two new callbacks:
cf_cb_file_closing (called before closing a capture file) cf_cb_file_closed will be called afterwards, but both only if a file is really closed as cf_close is called more often ...

If we are closing large capture files (~20MB), the screen looks ugly while the file is closed. Change this so the screen will immediately go back to initial state and a dialog (without buttons) is shown that the file is currently closed. As the operation which takes most of the time to close the file is a single eth_clist_clear call, we can't use a progress bar here.

cf_cb_live_capture_stopping: called when the user wants to stop the capture (toolbar or menu clicked). At least on Win32, the time between this and the actual stop completed can be noticeable (1-2 seconds), so the user doesn't know if the button press did anything at all. Do something similar as above, show a dialog box without buttons to inform that the close is in progress.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@15891 f5534014-38df-0310-8fa8-9805f1628bb7