tiff: fix include of windows.h on case-sensitive filesystems
tiff: fix include of windows.h on case-sensitive filesystems

On case-sensitive filesystems, such as when cross-compiling from Linux,
including Windows.h will result in an error.

GNOME/gdk-pixbuf,GNOME/gdk-pixbuf,GNOME/gdk-pixbuf,GNOME/gdk-pixbuf