fixing TTL to 2 per spec

the v1.1 upnp spec indicates that the default TTL should be set to 2
(and should also be configurable):

* http://upnp.org/specs/arch/UPnP-arch-DeviceArchitecture-v1.1.pdf

Author: wyattearp

libraries/ESP8266SSDP/ESP8266SSDP.cpp

@@ -51,7 +51,7 @@ extern "C" {
 #define SSDP_METHOD_SIZE  10
 #define SSDP_URI_SIZE     2
 #define SSDP_BUFFER_SIZE  64
-#define SSDP_MULTICAST_TTL 1
+#define SSDP_MULTICAST_TTL 2
 static const IPAddress SSDP_MULTICAST_ADDR(239, 255, 255, 250);