[mutter] prefs: fix a couple of typos

[Cosimo Cecchi <cosimoc src gnome org>]

commit 4c1fe4c30da48d8514a6fddec8cd2747d9aa717d
Author: Cosimo Cecchi <cosimo endlessm com>
Date:   Fri Jun 17 17:08:20 2016 -0700

    prefs: fix a couple of typos
    
    It's "threshold", not "trheshold". Also, make sure to add the enum value
    to the documentation section.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=767805

 src/core/prefs.c |    2 +-
 src/meta/prefs.h |    1 +
 2 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/src/core/prefs.c b/src/core/prefs.c
index 3ea5aa2..b6a8ab7 100644
--- a/src/core/prefs.c
+++ b/src/core/prefs.c
@@ -1844,7 +1844,7 @@ meta_preference_to_string (MetaPreference pref)
       return "DRAGGABLE_BORDER_WIDTH";
 
     case META_PREF_DRAG_THRESHOLD:
-      return "DRAG_TRHESHOLD";
+      return "DRAG_THRESHOLD";
 
     case META_PREF_DYNAMIC_WORKSPACES:
       return "DYNAMIC_WORKSPACES";
diff --git a/src/meta/prefs.h b/src/meta/prefs.h
index a0175ae..4394f74 100644
--- a/src/meta/prefs.h
+++ b/src/meta/prefs.h
@@ -64,6 +64,7 @@
  * @META_PREF_DRAGGABLE_BORDER_WIDTH: draggable border width
  * @META_PREF_AUTO_MAXIMIZE: auto-maximize
  * @META_PREF_CENTER_NEW_WINDOWS: center new windows
+ * @META_PREF_DRAG_THRESHOLD: drag threshold
  */
 
 /* Keep in sync with GSettings schemas! */