Change return 0, 1 to return S2N_SUCCESS, S2N_FAILURE

[maddeleine]

Problem:

We have a lot of s2n functions that indicate success by returning 0 and failure by returning 1. We should returning the S2N_SUCCESS/S2N_FAILURE consts since they are more readable and they exist.

Solution:

Change every return 0 to return S2N_SUCCESS; every return 1 to return S2N_FAILURE;

• Does this change what S2N sends over the wire? No
• Does this change any public APIs? No
• Which versions of TLS will this impact? N/A

Requirements / Acceptance Criteria:

• There is no more "return 0/1;" in the code
• Some sort of script is added to check for the presence of S2N_SUCCESS in every function. Not sure if we need a check for S2N_FAILURE.

• RFC links: N/A
• **Related Issues:**N/A
• Will the Usage Guide or other documentation need to be updated? No
• Testing: Our regular code suite.
  • Will this change trigger SAW changes? No
  • Should this change be fuzz tested? No

Out of scope:

N/A