Insert DER test data inside x509.uts and move it from scapy/layers/ to test/ (also, remove obsolete X.509 tests from test/regression.uts

As suggested by @guedou, this adds tests for fragment() and
defragment() functions.

--HG--
branch : ICMPv6NDOptDNSSL fixes

--HG--
branch : Support for DNS Search List Option in RA

--HG--
branch : Patch for PR#115

--HG--
branch : Patch for PR#82

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branch : homeplugav
rename : scapy/layers/HomePlugAV.py => scapy/contrib/HomePlugAV.py
rename : test/HomePlugAV.uts => scapy/contrib/HomePlugAV.uts

--HG--
branch : issue-5105

--HG--
branch : issue-5105

--HG--
branch : issue-5105

--HG--
branch : issue-5105

--HG--
branch : UTS fixes

--HG--
branch : homeplugav

--HG--
branch : ipsec

This patch adds a full implementation of the IPSec layer in
scapy/layers/ipsec.py. See the module's doc string for instructions.
In order to support encryption/decryption and authentication, the
pycrypto library is required. If not found, only the NULL/NULL
algorithms will be available.

(almost) complete test suite can be found in test/ipsec.uts and can
be launched with:

  ./bin/UTscapy -m scapy/layers/ipsec.py -t test/ipsec.uts -f text -F

Signed-off-by: Robin Jarry <robin.jarry@6wind.com>

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branch : ipsec

--HG--
branch : Issue #500

--HG--
branch : DNSSEC

Issues #884 & #915: IPv6 NA is not a NS & Error in class ICMPv6ND_NS(_ICMPv6NDGuessPayload, _ICMPv6, Packet):

Packet.build() is called only on the first layer. It will call
Packet.do_build() which will recurse through all layers. For each layer,
it will call Packet.self_build() which will do the job for each layer.
Packet.do_build() will call Packet.post_build() and transform on them,
and concatenate them. Then Packet.build() will call Packet.build_padding()
and Packet.build_done().

Note that this undetermined case will have a different behavior:
Raw("ABC")/Padding("abc")/Raw("DEF")/Padding("def")

It was "ABCabcDEFdef"
Now it is "ABCDEFabcdef"