handle extra warnings (#288)

src/core/net/ip6.cpp

@@ -307,7 +307,7 @@ exit:
 void Ip6::ProcessReceiveCallback(Message &aMessage)
 {
     ThreadError error = kThreadError_None;
-    Message *messageCopy;
+    Message *messageCopy = NULL;
 
     VerifyOrExit(sReceiveIp6DatagramCallback != NULL, ;);
 

third_party/mbedtls/mbedcrypto.c

@@ -35,6 +35,8 @@
  */
 #define MBED_MEMORY_BUF_SIZE  512
 
+void mbedInit(void);
+
 static bool sIsInitialized = false;
 static unsigned char sMemoryBuf[MBED_MEMORY_BUF_SIZE];