[1.9] String#chr fixes for the following tests:

String#chr returns a copy of self
String#chr returns a String
String#chr returns an empty String if self is an empty String
String#chr returns a 1-character String
String#chr returns the character at the start of the String
String#chr returns a String in the same encoding as self

kernel/common/string19.rb

@@ -631,4 +631,16 @@ def <<(other)
   end
   alias_method :concat, :<<
 
+  # Returns a one-character string at the beginning of the string.
+  #
+  #   a = "abcde"
+  #   a.chr    #=> "a"
+  def chr
+    if empty?
+      self
+    else
+      self[0]
+    end
+  end
+
 end

spec/tags/19/ruby/core/string/chr_tags.txt

@@ -1,8 +1,2 @@
-fails:String#chr returns a copy of self
-fails:String#chr returns a String
-fails:String#chr returns an empty String if self is an empty String
-fails:String#chr returns a 1-character String
-fails:String#chr returns the character at the start of the String
-fails:String#chr returns a String in the same encoding as self
 fails:String#chr understands multi-byte characters
 fails:String#chr understands Strings that contain a mixture of character widths