Fixed support for HTTP redirects on Windows
Fixed support for HTTP redirects on Windows

Also, since we didn't close the file handle in this case, and Windows
doesn't let you unlink open files, 0install actually reported a failure
to delete the temporary file instead of the real error. Fixed.

With --verbose, the error was:

info: Download failed: Invalid_argument("Unix.ftruncate not implemented")
Unix.Unix_error(Unix.EACCES, "unlink", "C:\\Users\\...\\0install-289dec-download")

fdopen/0install,HoMeCracKeR/0install,dbenamy/0install,DarkGreising/0install,DarkGreising/0install,bastianeicher/0install,fdopen/0install,dbenamy/0install,jaychoo/0install,HoMeCracKeR/0install,bartbes/0install,gfxmonk/0install,pombreda/0install,pombreda/0install,bastianeicher/0install,HoMeCracKeR/0install,pombreda/0install,bartbes/0install,dbenamy/0install,jaychoo/0install,fdopen/0install,bhilton/0install,DarkGreising/0install,gasche/0install,gasche/0install,gasche/0install,bastianeicher/0install,0install/0install,0install/0install,gfxmonk/0install,bhilton/0install,jaychoo/0install,0install/0install,bartbes/0install,bhilton/0install,gasche/0install,gfxmonk/0install