make these types future proof

Our core already supports more than 32k sheets and we should not use
sal_Int16 anymore for sheets.

Change-Id: Ifeb321cba044b255ef2e7d34da0908c27877d6ae

sc/source/filter/inc/worksheethelper.hxx

@@ -191,7 +191,7 @@ public:
     /** Returns the type of this sheet. */
     WorksheetType       getSheetType() const;
     /** Returns the index of the current sheet. */
-    sal_Int16           getSheetIndex() const;
+    sal_Int32           getSheetIndex() const;
     /** Returns the XSpreadsheet interface of the current sheet. */
     const ::com::sun::star::uno::Reference< ::com::sun::star::sheet::XSpreadsheet >&
                         getSheet() const;

sc/source/filter/oox/worksheethelper.cxx

@@ -219,7 +219,7 @@ public:
     /** Returns the type of this sheet. */
     inline WorksheetType getSheetType() const { return meSheetType; }
     /** Returns the index of the current sheet. */
-    inline sal_Int16    getSheetIndex() const { return maUsedArea.Sheet; }
+    inline sal_Int32    getSheetIndex() const { return maUsedArea.Sheet; }
     /** Returns the XSpreadsheet interface of the current sheet. */
     inline const Reference< XSpreadsheet >& getSheet() const { return mxSheet; }
 
@@ -1407,7 +1407,7 @@ WorksheetType WorksheetHelper::getSheetType() const
     return mrSheetGlob.getSheetType();
 }
 
-sal_Int16 WorksheetHelper::getSheetIndex() const
+sal_Int32 WorksheetHelper::getSheetIndex() const
 {
     return mrSheetGlob.getSheetIndex();
 }