Add functions to PacketListRecord to invalidate a single record's
colorization and column strings, used for a record is modified in a
way that needs to trigger redrawing, but we don't need to redraw
Move the functionality for adding, deleting, and setting frame comments
into PacketListModel, operating on QModelIndexes (or on all physical
rows in the case of deleting all comments from a file.) Trigger
recolorization of any record with an updated comment.
Only set a block as modified when deleting comments if we actually
deleted comments. This avoids marking a file as modified if we
delete all comments from all frames, or all comments from selected
frames, when those comments do not actually have frames.
If cf_set_modified_block is used to modify a block that is already
modified, it can't update the comment count. In that case, return
false and have the callers update the comment count. (It already
has a return value, which is always true.) This avoids having the
GUI warning about saving into a format that doesn't support comments
when comments have been added and then removed.
Note that, unlike with time references and time shifts, there
are no fields (and hence no columns nor color filters) that depend
on whether other fields have comments. If for some reason some
were added, then the model data for all frames would have to be
updated instead. Since there aren't, we don't need to
redrawVisiblePackets, but we do need to drawCurrentPacket to ensure
the packet details are redissected.