Fix for File.length() integer overflow on 32-bit Windows.
Fix for File.length() integer overflow on 32-bit Windows.

The File.length() method was returning a signed 32-bit value
on 32-bit Windows systems.  This was causing an integer overflow
on file sizes greater than 2 GB.  This appears to be caused by
the way Windows handles the STAT() function.  This patch checks
whether the current platform is Windows then uses the Windows API
to get the correct file size and return it as a jlong.

MaartenR/avian,lostdj/avian,minor-jason/avian,getlantern/avian,badlogic/avian,marcinolawski/avian,lwahlmeier/avian,getlantern/avian,lwahlmeier/avian,MaartenR/avian,ucdseniordesign/avian,ucdseniordesign/avian,lwahlmeier/avian,minor-jason/avian,lwahlmeier/avian,bgould/avian,lostdj/avian,dicej/avian,bgould/avian,joshuawarner32/avian,bgould/avian,ucdseniordesign/avian,bigfatbrowncat/avian-pack.avian,badlogic/avian,bigfatbrowncat/avian-pack.avian,ucdseniordesign/avian,bigfatbrowncat/avian-pack.avian,dicej/avian,marcinolawski/avian,bgould/avian,getlantern/avian,dicej/avian,minor-jason/avian,MaartenR/avian,marcinolawski/avian,joshuawarner32/avian,marcinolawski/avian,minor-jason/avian,bigfatbrowncat/avian-pack.avian,lostdj/avian,MaartenR/avian,lostdj/avian,dicej/avian,badlogic/avian,joshuawarner32/avian,badlogic/avian,joshuawarner32/avian,getlantern/avian