Allocate a new asynchronous wait context.
Declared in <openssl/async.h>
<openssl/async.h>
ASYNC_WAIT_CTX* ASYNC_WAIT_CTX_new();
Create one before ASYNC_start_job(); a context is associated with at most one ASYNC_JOB at a time but may be reused after that job finishes.
New ASYNC_WAIT_CTX, or NULL on allocation failure.