Fix GHC warning: -Wmissing-signatures

Related: https://github.com/xmonad/xmonad-contrib/issues/537

XMonad/Layout/StateFull.hs

@@ -64,6 +64,7 @@ type StateFull = FocusTracking Full
 
 -- | A pattern synonym for the primary use case of the @FocusTracking@
 --   transformer; using @Full@.
+pattern StateFull :: FocusTracking Full a
 pattern StateFull = FocusTracking Nothing Full
 
 instance LayoutClass l Window => LayoutClass (FocusTracking l) Window where

XMonad/Layout/TallMastersCombo.hs

@@ -366,6 +366,12 @@ focusWindow w s =
           Stack foc ls []
 
 -- | Merge two Maybe sublayouts.
+mergeSubLayouts
+  :: Maybe (l1 a)           -- ^ Left  layout
+  -> Maybe (l2 a)           -- ^ Right layout
+  -> TMSCombineTwo l1 l2 a  -- ^ How to combine the layouts
+  -> Bool                   -- ^ Return a 'Just' no matter what
+  -> Maybe (TMSCombineTwo l1 l2 a)
 mergeSubLayouts ml1 ml2 (TMSCombineTwo f w1 w2 vsp nmaster delta frac l1 l2) alwaysReturn =
   if alwaysReturn
   then Just $ TMSCombineTwo f w1 w2 vsp nmaster delta frac (maybe l1 id ml1) (maybe l2 id ml2)