WIP: Contribution of Adversarial Packet Testing Functionality to PacketDrill

[AmPaschal]

This pull request shows the changes we made to PacketDrill to support adversarial testing of Network Stacks.

Here are the significant files where changes were made

lexer.l, parser.y - Updated the Packetdrill grammer to support addition of mutation instructions (eg "{mut tcp data_offset 0x60}" says mutate the TCP data_offset field to 0x60)

fuzz_options.h, fuzz_options.c - Handles the creation of the fuzz_option struct that holds the mutation instruction defined in the Packetdrill script.

udp_packet.c, tcp_packet.c - Included the defined mutation instruction (if present) in the packet when creating a new packet struct.

fm_testing.c - Handles the mutation of the packet, following the defined mutation instruction. The actual mutation is implemented in a separate library that is loaded dynamically as a shared object file.

run.c - Added a perform_termination_handshake() function that sends a termination signal to the test target after each test, and waits for a response. This was necessary so the fuzzer can only start a new packetdrill test after it ensures the target has finished processing all packets of the current test.

run_packet.c - Added a send_test_complete_signal() function that generates and sends the termination signal.

logging.c - Created a die_free_so() function that frees the so_instance object before terminating a test. This is called when a test fails and informs the available so_instance to perform any cleanup operation it needs.

mutation-scripts directory - Contains sample Packetdrill with mutation instructions added.

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