crypto: don't build getLongID() with old gnutls

include/opendht/crypto.h

@@ -83,7 +83,9 @@ struct OPENDHT_PUBLIC PublicKey
     PublicKey& operator=(PublicKey&& o) noexcept;
 
     InfoHash getId() const;
+#if GNUTLS_VERSION_NUMBER >= 0x030401
     PkId getLongId() const;
+#endif
     bool checkSignature(const Blob& data, const Blob& signature) const;
     Blob encrypt(const Blob&) const;
 
@@ -362,7 +364,9 @@ struct OPENDHT_PUBLIC Certificate {
 
     /** Same as getPublicKey().getId() */
     InfoHash getId() const;
+#if GNUTLS_VERSION_NUMBER >= 0x030401
     PkId getLongId() const;
+#endif
 
     /** Read certificate Common Name (CN) */
     std::string getName() const;

include/opendht/securedht.h

@@ -51,10 +51,11 @@ public:
     InfoHash getId() const {
         return key_ ? key_->getPublicKey().getId() : InfoHash();
     }
+#if GNUTLS_VERSION_NUMBER >= 0x030401
     PkId getLongId() const {
         return key_ ? key_->getPublicKey().getLongId() : PkId();
     }
-
+#endif
     ValueType secureType(ValueType&& type);
 
     ValueType secureType(const ValueType& type) {

src/crypto.cpp

@@ -532,6 +532,7 @@ PublicKey::getId() const
     return id;
 }
 
+#if GNUTLS_VERSION_NUMBER >= 0x030401
 PkId
 PublicKey::getLongId() const
 {
@@ -541,6 +542,7 @@ PublicKey::getLongId() const
         return {};
     return h;
 }
+#endif
 
 Certificate::Certificate(const Blob& certData) : cert(nullptr)
 {
@@ -646,6 +648,7 @@ Certificate::getId() const
     return id;
 }
 
+#if GNUTLS_VERSION_NUMBER >= 0x030401
 PkId
 Certificate::getLongId() const
 {
@@ -657,6 +660,7 @@ Certificate::getLongId() const
         throw CryptoException("Can't get certificate public key ID.");
     return id;
 }
+#endif
 
 static std::string
 getDN(gnutls_x509_crt_t cert, const char* oid, bool issuer = false)