[gmime] Updated TODO

[Jeffrey Stedfast <fejj src gnome org>]

commit ec77ae46f0755dbb28edee3f15f6998f47a6cee3
Author: Jeffrey Stedfast <jestedfa microsoft com>
Date:   Mon Jan 30 12:24:25 2017 -0500

    Updated TODO

 TODO |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/TODO b/TODO
index 71c5a3c..e14f763 100644
--- a/TODO
+++ b/TODO
@@ -6,6 +6,9 @@ tasks are presented in.
 GMime 2.8 / 3.0 Planning:
 =========================
 
+- Drop the use of GMimeHeaderList's stream cache and instead solve
+  this problem by using a per-header cache of the original raw value.
+
 - Fix g_mime_message_[g,s]set_sender() to take/return an
   InternetAddressList to be more consistent with the recipient
   functions as well as being less error-prone.