Add logic for a better windows file identifier in tail.rb

Stat.ino always returns 0 on windows.  There has been a work around that create a checksum of the file name; however, this does not survive renames thus making log rollover a little trickier to configure.  This code uses FFI to make win32 calls to get a more appropriate file system identifier.  This identifier will survive renames and directory moves ( as long as it's not a volume move).    The inode variable was changed from an integer to a string due to this change.  

The output of the .sincedb will look like this:
2560502646-70822-1114112 0 2 142678

2560502646 - Volume Identifier
70822 - Low file number
1114112 - High File Number

More information on this can be found on MSDN,  scrolled down to the documentation on nFileIndexLow
http://msdn.microsoft.com/en-us/library/windows/desktop/aa363788(v=vs.85).aspx