Make sure yaca_*alloc() is not called with 0 size

Make sure yaca_*alloc() is not called with 0 size

- Add asserts
- Don't install static locks if CRYPTO_num_locks == 0
- Treat 0 output length as YACA_ERROR_INTERNAL:
  - If client provided a 0-length key we should detect it in yaca_sign_*init()
    and prevent him from using it. If it has 0 length in
    get_sign_output_length() it's an internal error.

Change-Id: I5d2d4063c568f76a25ee616b40c99abd5cc4dfa9