[gnome-builder] highlight-engine: fix -Wsign-compare warning

[Christian Hergert <chergert src gnome org>]

commit cc017aed794ecaa2042e039c8cffca57c2dc57d3
Author: Christian Hergert <chergert redhat com>
Date:   Tue Feb 28 12:03:52 2017 -0800

    highlight-engine: fix -Wsign-compare warning

 libide/highlighting/ide-highlight-engine.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/libide/highlighting/ide-highlight-engine.c b/libide/highlighting/ide-highlight-engine.c
index 440d51b..1ea13d3 100644
--- a/libide/highlighting/ide-highlight-engine.c
+++ b/libide/highlighting/ide-highlight-engine.c
@@ -49,7 +49,7 @@ struct _IdeHighlightEngine
   GSList              *private_tags;
   GSList              *public_tags;
 
-  guint64              quanta_expiration;
+  gint64               quanta_expiration;
 
   guint                work_timeout;