w32api:

* include/winioctl.h (FSCTL_SET_SPARSE): Define.

cygwin:

        * wincap.h (wincaps::supports_sparse_files): New flag.
        (wincapc::supports_sparse_files): New method.
        * wincap.cc (wincap_unknown): Define value for the new flag.
        (wincap_95): Ditto.
        (wincap_95osr2): Ditto.
        (wincap_98): Ditto.
        (wincap_98se): Ditto.
        (wincap_me): Ditto.
        (wincap_nt3): Ditto.
        (wincap_nt4): Ditto.
        (wincap_nt4sp4): Ditto.
        (wincap_2000): Ditto.
        (wincap_xp): Ditto.
        * path.h (path_conv::fs_flags): New method.
        * fhandler_disk_file.cc: Include winioctl.h for DeviceIoControl.
        (fhandler_disk_file::open): Set newly created and truncated files as
        sparse on platforms that support it.

winsup/cygwin/path.h

@@ -152,6 +152,7 @@ class path_conv
   short get_unitn () {return devn == FH_BAD ? 0 : unit;}
   DWORD file_attributes () {return fileattr;}
   DWORD drive_type () {return fs.drive_type;}
+  DWORD fs_flags () {return fs.flags;}
   BOOL fs_fast_ea () {return fs.sym_opt & PC_CHECK_EA;}
   void set_path (const char *p) {strcpy (path, p);}
   char *return_and_clear_normalized_path ();