wincrypt: Keyset does not exist about libcaes

[joachimmetz]

Per: https://docs.microsoft.com/en-us/windows/desktop/api/wincrypt/nf-wincrypt-cryptacquirecontexta

NTE_BAD_KEYSET
The key container could not be opened. A common cause of this error is that the key
container does not exist. To create a key container, call CryptAcquireContext using
the CRYPT_NEWKEYSET flag. This error code can also indicate that access to an existing
key container is denied. Access rights to the container can be granted by the key set
creator by using CryptSetProvParam.

Adding CRYPT_NEWKEYSET for the first call to CryptAcquireContext solves the issue.

[joachimmetz]

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