Treat 0x001f as 0x001e

Looking at the MS reference [1], 001E or 001F should be PT_STRING8.
Mapi::Types::DATA seems to ignore this. It sets 001f as PT_UNICODE, and
this sort of maps to the original filter converting to UTF8. I say
sort of, because I'm not sure how how Mapi::Types::DATA and
Mapi::Msg::PropertySTore::ENCODINGS interact.

This change at least makes both the existing and new spec pass ¯\_(ツ)_/¯

[1] https://msdn.microsoft.com/en-us/library/bb147591.aspx

Author: garethrees

lib/mapi/msg.rb

@@ -101,7 +101,7 @@ class PropertyStore
 			# change these to use mapi symbolic const names
 			ENCODINGS = {
 				0x000d =>   proc { |obj| obj }, # seems to be used when its going to be a directory instead of a file. eg nested ole. 3701 usually. in which case we shouldn't get here right?
-				0x001f =>   proc { |obj| Ole::Types::FROM_UTF16.iconv obj.read }, # unicode
+				0x001f =>   proc { |obj| obj.read.chomp 0.chr },
 				# ascii
 				# FIXME hack did a[0..-2] before, seems right sometimes, but for some others it chopped the text. chomp
 				0x001e =>   proc { |obj| obj.read.chomp 0.chr },

test/small-business-rates-relief.msg

@@ -35,6 +35,15 @@ def test_rendered_string_is_valid_encoding
     end
   end
 
+  def test_multipart_rendered_string_is_valid_encoding
+    msg = Mapi::Msg.open "#{TEST_DIR}/small-business-rates-relief.msg" do |msg|
+      string_version = msg.to_mime.to_s
+      if string_version.respond_to?(:valid_encoding?)
+        assert_equal true, string_version.valid_encoding?
+      end
+    end
+  end
+
   def test_embedded_msg_renders_as_string
     msg = Mapi::Msg.open "#{TEST_DIR}/embedded.msg" do |msg|
       assert_match "message/rfc822", msg.to_mime.to_s