Add a tcpdump-based L2listen socket

[Windows/Small fix] Add missing stop_filter

Removed outdated readfunc fonction

[Windows] Tiny fix to show error when interface does not exist

Switch from PyCrypto to Cryptography

This also includes some fixes for tcpdump()

Pypy won't run crypto tests on Travis CI because the cryptography
module cannot be installed with the Pypy version used.

See
  - https://github.com/pyca/cryptography/issues/2968 (discussion)
  - https://github.com/pyca/cryptography/issues/1141 (older)

Signed-off-by: Thomas Faivre <thomas.faivre@6wind.com>

Change the cryptographic library used in the following layers:
 * IPSec
 * TLS
 * Dot11

Notes:
 * Fix the WEP key in regression.uts: Should be a 40 bits key (5 ASCII)
   and 24 bits nonce for 64 bits WEP. The key was 8 ASCII => 88 bits
   in total
 * AES-GCM and AES-CMAC algorithms are now native in cryptography: add
   tests in ipsec.uts
 * cryptography only supports Python 2.6+
 * Fix the docstring for the pad method

Removed:
 * MD2 and MD4 hash algorithms for RSA in tls/crypto/pkcs1.py
 * AES-XCBC-96 not supported by cryptography.

Signed-off-by: Thomas Faivre <thomas.faivre@6wind.com>

The urandom function from the os package is a better RNG function than
the PyCrypto's Random.

Signed-off-by: Thomas Faivre <thomas.faivre@6wind.com>

Signed-off-by: Thomas Faivre <thomas.faivre@6wind.com>

[coverage] codecov appveyor support

Get constant values from "consts" since it is no longer in arch

Fix ls(): fix layer names and handle tuple default values (test added)

Add missing addr2 to block ack packet, improve addr2 validation performance.

[coverage] Add a codecov configuration file

Introduce tcpdump() function

[Windows] fix misplaced quotes

I had not tested it last time... 
When running  `python`, the first parameter is the file. So here all the arguments were passed as the file name...

One can now use tcpdump or tshark to dissect packets from
Scapy. This can help, for example, to check Scapy's dissectors

[coverage] codecov support

* bind vxlan-gpe over udp on port 4790

As defined here :
https://tools.ietf.org/html/draft-ietf-nvo3-vxlan-gpe-03#section-5.3



Signed-off-by: Gabriel Ganne <gabriel.ganne@qosmos.com>

* Typo fixed

Fix Windows bat files to work with spaces in paths (@gpotter2)