circular reference between libkrb5 and libk5crypto

[John Hascall]

> Clearly libkrb5 uses libk5crypto.
> 
> I seem to have created a case where libk5crypto wants to use libkrb5.
> In particular, as part of implementing a PRF, I called
> krb5_init_keyblock because I was setting up a derived key.
> 
> That ends up coming from libkrb5, which is probematiproblematic.
> 
> One proposal would be to move these routines into k5crypto.  I'm
> concerned that doing so would break our ABI on AIX and Debian (because
> of symbol versions).
> 
> I'm not sure what the right solution is besides that.

How about:
  1) Move krb5_init_keyblock;s code into k5crypto using some new function name
  2) Make krb5_init_keyblock (still in libkrb5) do nothing but call "1" above
  3) When in k5crypto call the new function name.
  4) Optionally phase out calls to krb5_init_keyblock over time.

John