Bignum: generate overflow checks for size_t
decode_value: check if program area sizes overflow
decode_value: check validity of refno
CritBit: do not cast through union
SSL.Constants: Added some missing CCM constants from RFC 6655.
Fix a an exception for client hello packages close to 512 bytes.
New temp assignment for padding extension. Added some RFC references.
Crypto.CTR.State: Added getter for the wrapped object.

The wrapped object is useful when extending the class (eg to
implement CCM it is needed to calculate the MAC).