Static ring::signature::RSA_PKCS1_SHA256

pub static RSA_PKCS1_SHA256: PKCS1 = PKCS1{digest_alg: &digest::SHA256,
      digestinfo_prefix: &SHA256_PKCS1_DIGESTINFO_PREFIX,}

PKCS#1 1.5 padding using SHA-256 for RSA signatures. Feature: rsa_signing.