ocfs2: Create ocfs2_stack_operations and split out the o2cb stack.

Define the ocfs2_stack_operations structure.  Build o2cb_stack_ops from
all of the o2cb-specific stack functions.  Change the generic stack glue
functions to call the stack_ops instead of the o2cb functions directly.

The o2cb functions are moved to stack_o2cb.c.  The headers are cleaned up
to where only needed headers are included.

In this code, stackglue.c and stack_o2cb.c refer to some shared
extern variables.  When they become modules, that will change.

Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>

fs/ocfs2/Makefile

@@ -25,6 +25,7 @@ ocfs2-objs := \
 	resize.o		\
 	slot_map.o 		\
 	stackglue.o		\
+	stack_o2cb.o		\
 	suballoc.o 		\
 	super.o 		\
 	symlink.o 		\