[gegl] Expand comment describing GeglOperationContext

[Øyvind Kolås <ok src gnome org>]

commit 0e1516c8f246a7d11af77cd74af09279b8aa45db
Author: �yvind Kolås <pippin gimp org>
Date:   Sun Oct 31 15:48:09 2010 +0000

    Expand comment describing GeglOperationContext

 gegl/operation/gegl-operation-context.h |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/gegl/operation/gegl-operation-context.h b/gegl/operation/gegl-operation-context.h
index 6e781b5..ef50e2a 100644
--- a/gegl/operation/gegl-operation-context.h
+++ b/gegl/operation/gegl-operation-context.h
@@ -27,7 +27,8 @@ G_BEGIN_DECLS
 /**
  * When a node in a GEGL graph does processing, it needs context such
  * as inputs. This structure holds this stuff and is passed to the
- * node during processing.
+ * node during processing. The data in a context is bound to one
+ * specific rendering/processing job/thread.
  */
 struct _GeglOperationContext
 {