Change shift expressions to unsigned types. Shifting signed values to

a result that is not representable has undefined behaviour.

code/qcommon/net_chan.c

@@ -52,7 +52,7 @@ to the new value before sending out any replies.
 #define	FRAGMENT_SIZE			(MAX_PACKETLEN - 100)
 #define	PACKET_HEADER			10			// two ints and a short
 
-#define	FRAGMENT_BIT	(1<<31)
+#define	FRAGMENT_BIT	(1U<<31)
 
 cvar_t		*showpackets;
 cvar_t		*showdrop;