More changes for KEX and ECDH. Set up hash descriptors, make ECC code work,

ses.hash and ses.session_id are now buffers (doesn't compile)

--HG--
branch : ecc

svr-kex.c

@@ -59,6 +59,7 @@ void recv_msg_kexdh_init() {
 		}
 	} else {
 #ifdef DROPBEAR_ECDH
+		buffer *ecdh_qs = buf_getstringbuf(ses.payload);
 #endif
 	}