CryptOpenAlgorithmProvider() documentation states:
"We recommend that you cache any algorithm provider handles that you will
use more than once, rather than opening and closing the algorithm providers
over and over."
This patch implements algorithm handle caching,
and also simplifies how hashes are handled in win_crypt.c
- MA_HASH_CTX* is now just BCrypt hash handle.
- We no longer allocate or free memory any memory outselves.
There are small change in the ma_hash API:
ma_hash_new() lost the second parameter, only used on Windows previously
