Multiple changes.

- Remove the runtime dependency on rake-compiler.
 - Use #rb_str_new instead of #rb_str_new2, the hash character array
   isn't null terminated.
 - Add various safeguards for object instantiations.
 - Remove the 'threaded' options for messages, folding them into
   'archived'.  If archiving is enabled, so is threading.
 - Return nil for lookups from the list object instead of raising
   exceptions.
 - Open subject indexes with the proper encodings (thanks Michael
   Granger!)
 - Allow touching and unlinking files to operate on multiple paths
   at once, within a single safety() wrap.

lib/ezmlm/list/message.rb

@@ -1,6 +1,7 @@
 #!/usr/bin/ruby
 # vim: set nosta noet ts=4 sw=4:
-#
+
+
 # An individual list message.
 #
 #    message = Ezmlm::List::Message.new( list, 24 )
@@ -31,6 +32,7 @@ class Ezmlm::List::Message
 	def initialize( list, message_number=0 )
 		raise ArgumentError, "Unknown list object." unless list.respond_to?( :listdir )
 		raise ArgumentError, "Invalid message number (impossible)" if message_number < 1
+		raise "Archiving is not enabled." unless list.archived?
 		raise ArgumentError, "Invalid message number (out of list bounds)" if message_number > list.message_count
 
 		@list = list