Allow tinc to be compiled without OpenSSL.

The option "--disable-legacy-protocol" was added to the configure
script. The new protocol does not depend on any external crypto
libraries, so when the option is used tinc is no longer linked to
OpenSSL's libcrypto.

src/connection.h

@@ -75,12 +75,15 @@ typedef struct connection_t {
 	struct node_t *node;            /* node associated with the other end */
 	struct edge_t *edge;            /* edge associated with this connection */
 
+#ifndef DISABLE_LEGACY
 	rsa_t *rsa;                     /* his public RSA key */
-	ecdsa_t *ecdsa;                 /* his public ECDSA key */
 	cipher_t *incipher;             /* Cipher he will use to send data to us */
 	cipher_t *outcipher;            /* Cipher we will use to send data to him */
 	digest_t *indigest;
 	digest_t *outdigest;
+#endif
+
+	ecdsa_t *ecdsa;                 /* his public ECDSA key */
 	sptps_t sptps;
 
 	int inmaclength;