Empy function args should specify a void

[toidiu]

Problem:

Old C compilers require specifying empty functions with a void arg. Some older functions are missing the void arg and should be updated: https://github.com/aws/s2n-tls/blob/main/crypto/s2n_openssl.h#L60-L62

bool s2n_libcrypto_is_awslc();

should be

bool s2n_libcrypto_is_awslc(void);

I havn't audited all functions so others might also exist.

Requirement

Wonder if there is a lint we can add to catch and prevent these.