This change adds a STACK_OF(CRYPTO_BUFFER) to an SSL_SESSION which
contains the raw form of the received certificates. The X509-based
members still exist, but their |enc| buffer will alias the
CRYPTO_BUFFERs.
The serialisation format of SSL_SESSIONs is also changed, in a backwards
compatible way. Previously, some sessions would duplicate the leaf
certificate in the certificate chain. These sessions can still be read,
but will be written in a way incompatible with older versions of the
code. This should be fine because the situation where multiple versions
exchange serialised sessions is at the server, and the server doesn't
duplicate the leaf certifiate in the chain anyway.
Change-Id: Id3b75d24f1745795315cb7f8089a4ee4263fa938
Reviewed-on: https://boringssl-review.googlesource.com/12163
Reviewed-by: Adam Langley <alangley@gmail.com>