chart2: avoid -Werror=deprecated-copy (GCC trunk towards GCC 9)

...by explicitly defaulting the copy/move functions (and, where needed in turn,
also a default ctor) for classes that have a user-declared dtor that does
nothing other than an implicitly-defined one would do, but needs to be user-
declared because it is virtual and potentially serves as a key function to
emit the vtable, or is non-public, etc.

Change-Id: Idecc69d147607824b95cd6fc715feb88c3fa1591
Reviewed-on: https://gerrit.libreoffice.org/58071
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

chart2/source/view/charttypes/CategoryPositionHelper.hxx

@@ -29,6 +29,11 @@ public:
     CategoryPositionHelper( double fSeriesCount, double CategoryWidth = 1.0);
     virtual ~CategoryPositionHelper();
 
+    CategoryPositionHelper(CategoryPositionHelper const &) = default;
+    CategoryPositionHelper(CategoryPositionHelper &&) = default;
+    CategoryPositionHelper & operator =(CategoryPositionHelper const &) = default;
+    CategoryPositionHelper & operator =(CategoryPositionHelper &&) = default;
+
     double getScaledSlotWidth() const;
     virtual double getScaledSlotPos( double fCategoryX, double fSeriesNumber ) const;
     void setCategoryWidth( double fCategoryWidth );