eliteforce: Revert "[qcommon] Remove dead serialization code"

This reverts commit d047210.

code/qcommon/msg.c

@@ -668,10 +668,55 @@ int MSG_HashKey(const char *string, int maxlen) {
 	return hash;
 }
 
+/*
+=============================================================================
+
+delta functions
+  
+=============================================================================
+*/
+
 extern cvar_t *cl_shownet;
 
 #define	LOG(x) if( cl_shownet && cl_shownet->integer == 4 ) { Com_Printf("%s ", x ); };
 
+void MSG_WriteDelta( msg_t *msg, int oldV, int newV, int bits ) {
+	if ( oldV == newV ) {
+		MSG_WriteBits( msg, 0, 1 );
+		return;
+	}
+	MSG_WriteBits( msg, 1, 1 );
+	MSG_WriteBits( msg, newV, bits );
+}
+
+int	MSG_ReadDelta( msg_t *msg, int oldV, int bits ) {
+	if ( MSG_ReadBits( msg, 1 ) ) {
+		return MSG_ReadBits( msg, bits );
+	}
+	return oldV;
+}
+
+void MSG_WriteDeltaFloat( msg_t *msg, float oldV, float newV ) {
+	floatint_t fi;
+	if ( oldV == newV ) {
+		MSG_WriteBits( msg, 0, 1 );
+		return;
+	}
+	fi.f = newV;
+	MSG_WriteBits( msg, 1, 1 );
+	MSG_WriteBits( msg, fi.i, 32 );
+}
+
+float MSG_ReadDeltaFloat( msg_t *msg, float oldV ) {
+	if ( MSG_ReadBits( msg, 1 ) ) {
+		floatint_t fi;
+
+		fi.i = MSG_ReadBits( msg, 32 );
+		return fi.f;
+	}
+	return oldV;
+}
+
 /*
 =============================================================================