Changed verify visibility from external to public

[Turupawn]

Made this change only on BaseStandardVerifier.sol and BaseUltraVerifier.sol solidity files. The IVerifier.sol interfaces should continue external as is expected from interfaces.

[Maddiaa0]

As the verifier uses hardcoded memory accesses ( and does not continue from the free memory pointer ), we do not want to enable contracts to inherit from the Verifier contacts, but for them to make an external library calls to them. This avoids situations where the verifier overwrites memory within the parent contract.

I'll make a note on the linked issue about how is best to call them

[Turupawn]

Oh I see, makes sense. Thanks for note!