* string.c (rb_str_upto): make next object before yield its block.

fix: can modify original begin string of String#upto.
  [ruby-dev:26384] [ruby-dev:39626] #2327

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@25632 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_string.rb

@@ -1602,6 +1602,17 @@ class TestString < Test::Unit::TestCase
     assert_equal(24, count, "[ruby-dev:39361]")
   end
 
+  def test_upto_nonalnum
+    first = S("\u3041")
+    last  = S("\u3093")
+    count = 0
+    assert_equal(first, first.upto(last) {|s|
+                   count += 1
+                   s.replace(last)
+                   })
+    assert_equal(83, count, "[ruby-dev:39626]")
+  end
+
   def test_mod_check
     assert_raise(RuntimeError) {
       s = ""