Remove last vestiges of generic tree_entry_list

Remove last vestiges of generic tree_entry_list

The old tree_entry_list is dead, long live the unified single tree
parser.

Yes, we now still have a compatibility function to create a bogus
tree_entry_list in builtin-read-tree.c, but that is now entirely local
to that very messy piece of code.

I'd love to clean read-tree.c up too, but I'm too scared right now, so
the best I can do is to just contain the damage, and try to make sure
that no new users of the tree_entry_list sprout up by not having it as
an exported interface any more.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>