WIP on bug #243, improvements on support of *splice/tee/sendfile

This is a work in progress on https://github.com/draios/sysdig/issues/243 .
More work is needed to declare the act of writing to fd_out at tee() and splice(), and act of reading from fd_at sendfile().
Please double-check the correctness of tables usage, I'm new to this project and may be wrong about some concepts.

P. S. Check jobs@draios.com inbox :)