HLSL: require tessellation factors to be fixed size arrays

SPIR-V requires that tessellation factor arrays be size 4 (outer) or 2 (inner).
HLSL allows other sizes such as 3, or even scalars.  This commit converts
between them by forcing the IO types to be the SPIR-V size, and allowing
copies between the internal and IO types to handle these cases.

hlsl/hlslParseHelper.h

@@ -248,6 +248,8 @@ protected:
     void addInterstageIoToLinkage();
     void addPatchConstantInvocation();
 
+    void fixBuiltInArrayType(TType&);
+
     void flatten(const TSourceLoc& loc, const TVariable& variable);
     int flatten(const TSourceLoc& loc, const TVariable& variable, const TType&, TFlattenData&, TString name);
     int flattenStruct(const TSourceLoc& loc, const TVariable& variable, const TType&, TFlattenData&, TString name);