Fix for strict aliasing rules.

* cipher/rijndael.c (do_setkey, prepare_decryption): Use u32_a_t for
casting.
--

gcc 4.7.1 now show warnings for more functions.  Like:

  rijndael.c:412:19: warning: dereferencing type-punned pointer will
  break strict-aliasing rules [-Wstrict-aliasing]

This fixes them using the may_alias attribute.
Speed up GOST 34.11 significantly

* cipher/gost28147.c, cipher/gost.h: provide internal interface to gost
  encryption for one block.
* cipher/gost3411.c: use backdoor to skip going through gcrypt cipher
  layers.

Signed-off-by: Dmitry Eremin-Solenikov <dmitry_eremin@mentor.com>