Real conversion to 32bit dev_t.  Expansion to:
	* mknod() - 32
	* newstat() - 32 on 64bit platforms
	* stat64() - 32 on mips, 64 on everything else (mips has weird struct
stat64 and can't get more than 32 bits).  Note that right now the difference
is purely theoretical - we don't have internal values above 32 bits, so
huge_... vs. new_... only marks the places where 64bit conversion will need
extra work.
	* arch-dependent stat variants - depending on width available.
	* ustat et.al. - 32
	* filesystems that can handle 32 bits right now - 32
	* ext2 and ext3 - 32, with large dev_t inodes having 0 in the first
element of i_data[] (where we store dev_t value for small device numbers) and
keeping the value in the second element.
	* nfsd - 32; it can be driven to 64, but we'll get several issues with
NFSv2 support.
	* RAID - 32
	* devmapper - with v1 it's still 16 (nothing to do here), with v4 it's
64.
	* loop - 64
	* initramfs - 32
	* do_mounts code - 32.  Parts that scan devfs tree are using newstat()
on 64bit platforms and stat64() on the rest (IOW, the latest stat variant on
given platform).
	* old_valid_dev()/new_valid_dev() added where needed (stat variants,
mostly - we fail with -EOVERFLOW if values do not fit).