reiserfs: cleanup, rename key and item accessors to more friendly names

This patch does a quick search and replace:
B_N_PITEM_HEAD() -> item_head()
B_N_PDELIM_KEY() -> internal_key()
B_N_PKEY() -> leaf_key()
B_N_PITEM() -> item_body()

And the item_head version:
B_I_PITEM() -> ih_item_body()
I_ENTRY_COUNT() -> ih_entry_count()

And the treepath variants:
get_ih() -> tp_item_head()
PATH_PITEM_HEAD() -> tp_item_head()
get_item() -> tp_item_body()

... which makes the code much easier on the eyes.

I've also removed a few unused macros.

Checkpatch will complain about the 80 character limit for do_balan.c.
I've addressed that in a later patchset to split up balance_leaf().

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/reiserfs/bitmap.c b/fs/reiserfs/bitmap.c
index dc9a682..c3de650 100644
--- a/fs/reiserfs/bitmap.c
+++ b/fs/reiserfs/bitmap.c
@@ -819,9 +819,9 @@
 	path = hint->path;
 	bh = get_last_bh(path);
 	RFALSE(!bh, "green-4002: Illegal path specified to get_left_neighbor");
-	ih = get_ih(path);
+	ih = tp_item_head(path);
 	pos_in_item = path->pos_in_item;
-	item = get_item(path);
+	item = tp_item_body(path);
 
 	hint->search_start = bh->b_blocknr;