Fix compilation error with gcc 11

error: loop variable 'verification_pair' creates a copy from type 'const std::pair<bool (*)(const jwt::claim&, void*), void*>' [-Werror=range-loop-construct]

Author: ellert

src/scitokens_internal.h

@@ -390,7 +390,7 @@ class Validator {
                  }
              }
              // std::cout << "Running claim " << claim_pair.first << " through validation." << std::endl;
-             if (iter != m_validators.end()) for (const auto verification_func : iter->second) {
+             if (iter != m_validators.end()) for (const auto &verification_func : iter->second) {
                  const jwt::claim &claim = jwt.get_payload_claim(claim_pair.first);
                  if (claim.get_type() != jwt::claim::type::string) {
                      std::stringstream ss;
@@ -409,7 +409,7 @@ class Validator {
                      }
                  }
              }
-             if (iter_claim != m_claim_validators.end()) for (const auto verification_pair : iter_claim->second) {
+             if (iter_claim != m_claim_validators.end()) for (const auto &verification_pair : iter_claim->second) {
                  const jwt::claim &claim = jwt.get_payload_claim(claim_pair.first);
                  if (verification_pair.first(claim, verification_pair.second) == false) {
                      std::stringstream ss;