Embed one of those structures in a capture_file, and have a struct
epan_session point to that structure rather than to a capture_file.
Pass that structure to the routines that fetch data that libwireshark
uses when dissecting.
That separates the stuff that libwireshark expects from the stuff that
it doesn't look at.
Change-Id: Ia3cd28efb9622476437a2ce32204597fae720877
Reviewed-on: https://code.wireshark.org/review/24692
Reviewed-by: Guy Harris <guy@alum.mit.edu>