[PATCH] ext4: enable building of ext4

Originally part of a patch from Mingming Cao and Randy Dunlap.  Reorganized
by Shaggy.

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Mingming <Cao&lt;cmm@us.ibm.com>
Signed-off-by: Dave Kleikamp <shaggy@austin.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>