docs for creating arrays

* array.c: [DOC] add example for Array.new with block and index.
  Reported by Don Cruickshank.  [ruby-core:68442] [Bug #10944]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58037 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

array.c

@@ -5927,6 +5927,7 @@ rb_ary_sum(int argc, VALUE *argv, VALUE ary)
  *  other arrays:
  *
  *     Array.new(4) { Hash.new }  #=> [{}, {}, {}, {}]
+ *     Array.new(4) {|i| i.to_s } #=> ["0", "1", "2", "3"]
  *
  *  This is also a quick way to build up multi-dimensional arrays:
  *