Fixes ticket:110 (more UTF-16 problems)

Missing include for UndefinedNamespaceException was causing errors in some
    cases.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@13816 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/rexml/encoding.rb

@@ -56,8 +56,13 @@ module REXML
 
     def check_encoding str
       # We have to recognize UTF-16, LSB UTF-16, and UTF-8
-      return UTF_16 if /\A\xfe\xff/n =~ str
-      return UNILE if /\A\xff\xfe/n =~ str
+      if str[0] == 0xfe && str[1] == 0xff
+        str[0,2] = ""
+        return UTF_16
+      elsif str[0] == 0xff && str[1] == 0xfe
+        str[0,2] = ""
+        return UNILE
+      end
       str =~ /^\s*<\?xml\s+version\s*=\s*(['"]).*?\1\s+encoding\s*=\s*(["'])(.*?)\2/um
       return $3.upcase if $3
       return UTF_8