If we do a Save or Save As with a move, don't reread the capture file,

If we do a Save or Save As with a move, don't reread the capture file,
just tweak the elements in the capture_file structure as necessary and
poke the UI to update stuff such as the windows title.

If we do a Save or Save As with a copy, don't reread the capture file,
just close the old wtap, open a wtap for the copy, and tweak the
elements in the capture_file structure as necessary and poke the UI to
update stuff such as the windows title.

Otherwise, don't do a full read-and-dissect pass on the capture file,
just close the old wtap, open a wtap for the new file, tweak the
elements in the capture_file structure as necessary and poke the UI to
update stuff such as the windows title, and rescan the file to update
the packet offsets (and cause Wiretap to regenerate, for a gzipped file,
the information needed to support fast random access to the gzipped
file).

This should speed up Save and Save As a bit, as well as removing some
glitches in the UI (e.g., you won't see the packet list disappear and
reappear).

svn path=/trunk/; revision=43101