...contrary to what c511c65434 "tdf#146619 Use
more forward declarations in include/tools" apparently assumed, as seen at least
with recent Clang 23 trunk against recent libstdc++ 16 trunk,
> In file included from tools/source/generic/poly2.cxx:22:
> In file included from tools/inc/poly.h:22:
> In file included from ~/gcc/inst/lib/gcc/x86_64-pc-linux-gnu/16.0.1/../../../../include/c++/16.0.1/memory:80:
> ~/gcc/inst/lib/gcc/x86_64-pc-linux-gnu/16.0.1/../../../../include/c++/16.0.1/bits/unique_ptr.h:131:18: error: invalid application of 'sizeof' to an incomplete type 'Point'
> 131 | static_assert(sizeof(_Tp)>0,
> | ^~~~~~~~~~~
> ~/gcc/inst/lib/gcc/x86_64-pc-linux-gnu/16.0.1/../../../../include/c++/16.0.1/bits/unique_ptr.h:684:4: note: in instantiation of function template specialization 'std::default_delete<Point[]>::operator()<Point>' requested here
> 684 | get_deleter()(__ptr);
> | ^
> tools/inc/poly.h:33:21: note: in instantiation of member function 'std::unique_ptr<Point[]>::~unique_ptr' requested here
> 33 | ImplPolygon() : mnPoints(0) {}
> | ^
> include/tools/poly.hxx:60:7: note: forward declaration of 'Point'
> 60 | class Point;
> | ^
Change-Id: I0b96222dcec7e98b974151004248a91ba1854e60
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/198573
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <stephan.bergmann@collabora.com>