"data source" has a name and a top-level tvbuff, and frames can have a
list of data sources associated with them.
Use the tvbuff pointer to determine which data source is the data source
for a given field; this means we don't have to worry about multiple data
sources with the same name - the only thing the name does is label the
notebook tab for the display of the data source, and label the hex dump
of the data source in print/Tethereal output.
Clean up a bunch of things discovered in the process of doing the above.
svn path=/trunk/; revision=4749
structure to the "packet_info" structure; only stuff that's permanently
stored with each frame should be in the "frame_data" structure, and the
"column_info" structure is not guaranteed to hold the column values for
that frame at all times - it was only in the "frame_data" structure so
that it could be passed to dissectors, and, as all dissectors are now
passed a pointer to a "packet_info" structure, it could just as well be
put in the "packet_info" structure.
That saves memory, by shrinking the "frame_data" structure (there's one
of those per frame), and also lets us clean up the code a bit.
svn path=/trunk/; revision=4370
