hashtable for association token -> mptcpConnection

the hashtable is a table of 'struct list_head' indexed by the token's hash.
Each is referenced by a 'struct nf_mptcp_conn' containing the information about
the connection associated to the token.
premises of join_related and merge

nf_conntrack_in: set an expectation for join segments with right token
- added token in mptcp tuple
- new hash table of nf_mptcp_conn's (using struct list_head)
- [new proto file for mptcp conntrack's handling -- shouldn't be used as such]

+ merge branch 'develop' into join_related
draft MP_JOIN support

Still does not seem to work :( Further tests needed.
- mp_join packets marked as RELATED
- modification of tcp_new (from nf_conntrack_proto_tcp.c) to handle MPTCP
- permit nf_conntrack_mptcp's compilation as module by using dummy default
  implementations of nf_ct_mptcp_new and nf_mptcp_get_ptr
- using a new structure nf_conn_mptcp to store connections properties
dirty fix to make work the match

The match was no longer working because the nf_mptcp_get_ptr implementation
wasn't working while being compiled in a module. Dunno why yet.
Trying the trampoline solution given here:
http://stackoverflow.com/questions/11463184/how-to-use-exported-symbols-in-the-linux-kernel
makes the kernel oops...
So, this puts the function in the header used by all mptcp related stuff in
netfilter. It's not very pretty but it works atm.
base design: new conditional fields in nf_conn

added struct nf_conn_mptcp* and struct mptcp_subflow_info to nf_conn when
NF_CONNTRACK_MPTCP is compiled.
join/related working!

with nf_ct_mptcp_new as a trampoline function, calling the real implementation
from the module nf_conntrack_mptcp only when the latter is loaded.
mptcp connection tracking -- start
ct: some cleaning for new FSM implem

- mpmaster pointer now in tcp-specific data structs
- removing helper remainings
- removing commented unuseful stuff
- fixing pointer issue and params of get_conntrack_index()
ct: mptcp_packet handling premises
ct: adding hook for mptcp_packet into proto_tcp
ct: fix several compile errors
pre-eclipse
git backup before big changes
no more compilable as a module
mptcp fsm, subflow fsm (tcp one accessible)
new organization + timers :)

- todo: hashtable !
various fixes
compiles correctly.
match + various fixes

- match: new flags
- find_join -> find_subtype
- compilation dependency for nf_mptcp_common.c
xt_connlimit: support for limit of subflows