In 94cee4a4 I overlooked that config.h
unconditionally sets _FILE_OFFSET_BITS, so it cannot be used to detect
MinGW W64 environment. It looks like Emacs folks already found
solution; instead of _FILE_OFFSET_BITS use _W64 as suggested in
http://lists.gnu.org/archive/html/emacs-devel/2013-03/msg00723.html

Use _FILE_OFFSET_BITS macro to distinguish between native MinGW and
32 bit under MinGW-64. The latter does not require fseeko/ftello
redefinition which it already does in case of _FILE_OFFSET_BITS=64.

We need to hide "modprobe efivars" error output to avoid confusion. So
consolidate grub_util_exec_* into single function that can optionally redirect
all three standard descriptors and make all other functions compatibility
wrappers.

Also remove include/grub/osdep/exec_unix.h which does not appear to be used
anywhere.

	Fixes build for windows.

	the function of these files exceeds what can be sanely handled in shell
	in posix-comaptible way. Also writing it in C extends the functionality
	to non-UNIX-like OS and minimal environments.

	mingw32.

	%llx/%llu.

	* grub-core/gnulib/msvc-inval.c: Use __cdecl rather than cdecl.
	* grub-core/lib/posix_wrap/wchar.h: Define wint_t.
	* grub-core/lib/posix_wrap/wctype.h: Define wctype_t.
	* include/grub/osdep/hostfile_windows.h: Don't define fseeko/ftello
	on mingw64.
	* include/grub/types.h: Allow sizeof (long) != sizeof (void *).

	closedir to handle filename charset translation.

	missing prototype.
	(grub_util_tchar_to_utf8): Likewise.