Instead of using a Boolean for the search direction, use an enum, so

Instead of using a Boolean for the search direction, use an enum, so
that you can tell from examination whether the search is forward or
backward.

Make the cf_find_packet routines take the direction as an explicit
argument, rather than, in the cases where you don't want to permanently
set the direction, saving the direction in the capture_file structure,
changing it, doing the search, and restoring the saved direction.  Give
more information in the Doxygen comments for those routines.

Add a cf_find_packet_dfilter_string() routine, which takes a filter
string rather than a compiled filter as an argument.  Replace
find_previous_next_frame_with_filter() with it.

Have cf_read_frame_r() and cf_read_frame() pop up the error dialog if
the read fails, rather than leaving that up to its caller.  That lets us
eliminate cf_read_error_message(), by swallowing its code into
cf_read_frame_r().  Add Doxygen comments for cf_read_frame_r() and
cf_read_frame().

Don't have find_packet() read the packet before calling the callback
routine; leave that up to the callback routine.

Add cf_find_packet_marked(), to find the next or previous marked packet,
and cf_find_packet_time_reference(), to find the next or previous time
reference packet.  Those routines do *not* need to read the packet data
to see if it matches; that lets them run much faster.

Clean up indentation.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@33791 f5534014-38df-0310-8fa8-9805f1628bb7