Remove Dirent#children=.

Only had one caller, and was subtly broken for general use due to not
clearing @name_lookup.

lib/ole/storage/base.rb

@@ -135,7 +135,7 @@ class << @dirents
 				def to_tree idx=0
 					return [] if idx == Dirent::EOT
 					d = self[idx]
-					d.children = to_tree d.child
+					to_tree(d.child).each { |child| d << child }
 					raise FormatError, "directory #{d.inspect} used twice" if d.idx
 					d.idx = idx
 					to_tree(d.prev) + [d] + to_tree(d.next)
@@ -786,11 +786,6 @@ def name= name
 				@name = name
 			end
 
-			def children= children
-				@children = []
-				children.each { |child| self << child }
-			end
-
 			def open mode='r'
 				raise Errno::EISDIR unless file?
 				io = RangesIOMigrateable.new self, mode