eliminate use of stat()
platform-specific code for determining file size

 - use stat() on POSIX platforms
 - use GetFileSizeEx() on WinNT platforms
bugfix: add fileno() call in POSIX getFileSize()
bugfix: fix filesize check for 64bit platforms
Merge branch 'master' of https://github.com/Zirias/c64_tool_mkd64 into perl