math/cgal: fix headers for use with clang 19

Clang 19 has become more strict about errors in member functions, which
results in errors building ports that use headers from math/cgal, such
as cad/csxcad:

  In file included from /wrkdirs/usr/ports/cad/csxcad/work/CSXCAD-0.6.3/src/CSPrimPolyhedron.cpp:25:
  In file included from /wrkdirs/usr/ports/cad/csxcad/work/CSXCAD-0.6.3/src/CSPrimPolyhedron_p.h:6:
  In file included from /usr/local/include/CGAL/Polyhedron_3.h:25:
  In file included from /usr/local/include/CGAL/HalfedgeDS_default.h:23:
  In file included from /usr/local/include/CGAL/boost/graph/graph_traits_HalfedgeDS_default.h:15:
  In file included from /usr/local/include/CGAL/boost/graph/graph_traits_HalfedgeDS.h:29:
  /usr/local/include/CGAL/boost/graph/iterator.h:224:22: error: no member named 'base' in 'Halfedge_around_source_iterator<Graph>'
    224 |     return (! (this->base() == nullptr)) ?
        |                ~~~~  ^
  /usr/local/include/CGAL/boost/graph/iterator.h:324:22: error: no member named 'base' in 'Halfedge_around_target_iterator<Graph>'
    324 |     return (! (this->base() == nullptr)) ?
        |                ~~~~  ^
  /usr/local/include/CGAL/boost/graph/iterator.h:423:22: error: no member named 'base' in 'Halfedge_around_face_iterator<Graph>'
    423 |     return (! (this->base() == nullptr)) ?
        |                ~~~~  ^

The problem is that the `base()` member function is only available when
an iterator is derived from `boost::iterator_adaptor`, but the three
iterators mentioned above, `Halfedge_around_source_iterator`,
`Halfedge_around_target_iterator` and `Halfedge_around_face_iterator`
are not.

Upstream CGAL has done a bit more refactoring in this particular area,
but is enough to cherry-pick the changes that remove the `operator
bool_type() const` member functions, which reference the non-existing
`base()` member function.

Bump PORTREVISION to ensure dependent ports build against the fixed
headers.

PR:		281880
Approved by:	maintainer timeout (2 weeks)
MFH:		2024Q4

(cherry picked from commit 54b05f1c)