Fix a buffer overflow on platforms where sizeof(long) > sizeof(int).
https://bugs.gentoo.org/show_bug.cgi?id=329031

--- libvncserver/tightvnc-filetransfer/filetransfermsg.c
+++ libvncserver/tightvnc-filetransfer/filetransfermsg.c
@@ -393,7 +393,8 @@
 CreateFileDownloadZeroSizeDataMsg(unsigned long mTime)
 {
 	FileTransferMsg fileDownloadZeroSizeDataMsg;
-	int length = sz_rfbFileDownloadDataMsg + sizeof(int);
+	uint32_t mTime32 = (uint32_t)mTime;
+	int length = sz_rfbFileDownloadDataMsg + sizeof(mTime32);
 	rfbFileDownloadDataMsg *pFDD = NULL;
 	char *pFollow = NULL;
 	
@@ -413,7 +414,7 @@
 	pFDD->compressedSize = Swap16IfLE(0);
 	pFDD->realSize = Swap16IfLE(0);
 	
-	memcpy(pFollow, &mTime, sizeof(unsigned long));
+	memcpy(pFollow, &mTime, sizeof(mTime32));
 
 	fileDownloadZeroSizeDataMsg.data	= pData;
 	fileDownloadZeroSizeDataMsg.length	= length;