Add incremental CCM authentication processing

[pascal-brand38]

CCM is only meant for packet mode where the length of the input is known in
advance. Since it is a packet mode function, CCM only had one function that
performs the protocol.

However, incremental authentication is usefull in some usecases. It also
ensure some kind of coherencies when processing with a given authentication
mode or another. To achieve this aim, this commit adds the following functions:
ccm_init()
ccm_add_aad()
cm_add_nonce()
ccm_process()
ccm_done()
ccm_reset()
as well as the data structure
ccm_state

Change-Id: I5225a42bb098708c4af07518b561bb00f85bc243

[pascal-brand38]

Did anyone get a chance to look at it?
Thanks.

[sjaeckel]

Yeah I did and that's the result :(

mac_test......
185: x=0 y=1
tag is     contents: 
7c 20 51 a7 ae 20 0b cf 
tag should contents: 
17 e8 d1 2c fd f9 26 e0 
Algorithm failed test vectors. (5)
mac_test.c:31:ccm_test()

Probably I got something wrong?
The testvectors should be fine as they're from NIST

[sjaeckel]

please find my changes here

[sjaeckel]

Would you mind adding documentation please?

[pascal-brand38]

Pull-request proposed at #56