fix LdapPduError uninitialized constant

Author: ggalancs

lib/net/ldap/pdu.rb

@@ -123,7 +123,7 @@ def initialize(ber_object)
     when ExtendedResponse
       parse_extended_response(ber_object[1])
     else
-      raise LdapPduError.new("unknown pdu-type: #{@app_tag}")
+      raise LdapError.new("unknown pdu-type: #{@app_tag}")
     end
 
     parse_controls(ber_object[2]) if ber_object[2]

lib/net/ldap/version.rb

@@ -1,5 +1,5 @@
 module Net
   class LDAP
-    VERSION = "0.16.2"
+    VERSION = "0.16.21"
   end
 end