Instead of allocating a separate mutex object on the heap,
include the HEIMDAL_MUTEX in the krb5_context structure.
Change-Id: If6db484177410487176985e43e3b43e0f2166518
lib/krb5/crypto.c was a large, monolithic block of code which made
it very difficult to selectively enable and disable particular
alogrithms.
Reorganise crypto.c into individual files for each encryption and
salt time, and place the structures which tie everything together
into their own file (crypto-algs.c)
Add a non-installed library (librfc3961) and test program
(test_rfc3961) which builds a minimal rfc3961 crypto library, and
checks that it is usable.
