libnetconf2 UPDATE merge SSH and TLS req into one

In this commit I made the changes that if you want to use TLS, you have
to have both OpenSSL and libssh installed and viceversa. Set the minimum
required OpenSSL version to 3.0 and 0.9.5 for libssh.
diff --git a/src/session.h b/src/session.h
index eb3b36f..5f256ec 100644
--- a/src/session.h
+++ b/src/session.h
@@ -23,7 +23,7 @@
 
 #include "netconf.h"
 
-#ifdef NC_ENABLED_SSH
+#ifdef NC_ENABLED_SSH_TLS
 
 /**
  * @brief Enumeration of NETCONF SSH authentication methods
@@ -45,10 +45,6 @@
     NC_SSH_KNOWNHOSTS_SKIP          /**< do not add a known_hosts entry and skip all host key checks */
 } NC_SSH_KNOWNHOSTS_MODE;
 
-#endif /* NC_ENABLED_SSH */
-
-#ifdef NC_ENABLED_TLS
-
 /**
  * @brief Enumeration of cert-to-name mapping types
  */
@@ -62,7 +58,7 @@
     NC_TLS_CTN_COMMON_NAME      /**< common name as username */
 } NC_TLS_CTN_MAPTYPE;
 
-#endif /* NC_ENABLED_TLS */
+#endif /* NC_ENABLED_SSH_TLS */
 
 /**
  * @brief Enumeration of possible session statuses
@@ -83,12 +79,11 @@
     NC_TI_FD,         /**< file descriptors - use standard input/output, transport protocol is implemented
                            outside the current application */
     NC_TI_UNIX,       /**< unix socket */
-#ifdef NC_ENABLED_SSH
+#ifdef NC_ENABLED_SSH_TLS
     NC_TI_LIBSSH,     /**< libssh - use libssh library, only for NETCONF over SSH transport */
-#endif
-#ifdef NC_ENABLED_TLS
+
     NC_TI_OPENSSL     /**< OpenSSL - use OpenSSL library, only for NETCONF over TLS transport */
-#endif
+#endif /* NC_ENABLED_SSH_TLS */
 } NC_TRANSPORT_IMPL;
 
 /**
@@ -234,20 +229,6 @@
  */
 void nc_session_free(struct nc_session *session, void (*data_free)(void *));
 
-#if defined (NC_ENABLED_SSH) || defined (NC_ENABLED_TLS)
-
-/**
- * @brief Free all the dynamically allocated thread-specific libssl/libcrypto
- * resources.
- *
- * This function should be called only if init (nc_client_init(), respectively nc_server_init()) was called.
- * Call it in every thread your application creates just before the thread exits. In the last thread
- * (usually the main one) call nc_client_destroy(), respectively nc_server_destroy().
- */
-void nc_thread_destroy(void);
-
-#endif /* NC_ENABLED_SSH || NC_ENABLED_TLS */
-
 #ifdef __cplusplus
 }
 #endif