This adds Atalla support code to the ENGINE framework. If you have an

Atalla card, you should be able to compile with the "hw-atalla" switch
with "./config" or "perl Configure", and then you can use the command-
line switch "-engine atalla" inside speed, s_cient and s_server (after
checking out note (1)).

Notes:
  (1) I've turned on native name translation when loading the shared-
      library, but this means that the Unix shared library needs to be
      libatasi.so rather than atasi.so. I got around this in my testing
      by creating a symbollic link from /usr/lib/libatasi.so to the real
      library, but something better will be needed. It also assumes in
      win32 that the DLL will be called atasi.dll - but as I don't have
      a win32/atalla environment to try I have no idea yet if this is
      the case.
  (2) Currently DSA verifies are not accelerated because I haven't yet
      got a mod_exp-based variant of BN_mod_exp2_mont() that yields
      correct results.
  (3) Currently the "init()" doesn't fail if the shared library can
      load successfully but the card is not operational. In this case,
      the ENGINE_init() call will succeed, but all RSA, DSA, DH, and
      the two BN_*** operations will fail until the ENGINE is switched
      back to something that does work. I expect to correct this next.
  (4) Although the API for the Atalla card just has the one crypto
      function suggesting an RSA private key operation - this is in
      fact just a straight mod_exp function that ignores all the RSA
      key parameters except the (private) exponent and modulus. This is
      why the only accelerator work is taking place inside the mod_exp
      function and there's no optimisation of RSA private key operations
      based on CRT etc.