Changed the fallback String#each_char to use valid 1.9 syntax.

Signed-off-by: Jeremy Kemper <jeremy@bitsweat.net>

activesupport/lib/active_support/core_ext/string/iterators.rb

@@ -13,7 +13,9 @@ module ActiveSupport #:nodoc:
         # When $KCODE = 'UTF8', multi-byte characters are yielded appropriately.
         def each_char
           scanner, char = StringScanner.new(self), /./mu
-          loop { yield(scanner.scan(char) || break) }
+          while c = scanner.scan(char)
+            yield c
+          end
         end
       end
     end