[aat] Fix some struct sizes

I hate it that with my compiler at least, it doesn't catch totally uncompilable
statements in templates if they are not used...

src/hb-aat-layout-common-private.hh

@@ -602,7 +602,7 @@ struct StateTable
 		entryTable;	/* Offset to the entry array. */
 
   public:
-  DEFINE_SIZE_UNION (2, format);
+  DEFINE_SIZE_STATIC (16);
 };
 
 template <typename EntryData>

src/hb-aat-layout-morx-table.hh

@@ -169,7 +169,7 @@ struct RearrangementSubtable
   protected:
   StateTable<void>	machine;
   public:
-  DEFINE_SIZE_MIN (2);
+  DEFINE_SIZE_STATIC (16);
 };
 
 struct ContextualSubtable
@@ -283,7 +283,7 @@ struct ContextualSubtable
   OffsetTo<UnsizedOffsetListOf<Lookup<GlyphID>, HBUINT32>, HBUINT32>
 			substitutionTables;
   public:
-  DEFINE_SIZE_MIN (2);
+  DEFINE_SIZE_STATIC (20);
 };
 
 struct LigatureSubtable
@@ -436,7 +436,7 @@ struct ChainSubtable
   InsertionSubtable		insertion;
   } u;
   public:
-  DEFINE_SIZE_MIN (2 * sizeof (HBUINT32) + 4);
+  DEFINE_SIZE_MIN (12);
 };
 
 struct Chain
@@ -488,7 +488,7 @@ struct Chain
   // subtableGlyphCoverageArray if major == 3
 
   public:
-  DEFINE_SIZE_MIN (8 + 2 * sizeof (HBUINT32));
+  DEFINE_SIZE_MIN (16);
 };