[multi precision] avoid constexpr which is not supported by boost multiprecision

Author: barendgehrels

include/boost/geometry/algorithms/detail/buffer/line_line_intersection.hpp

@@ -77,7 +77,7 @@ struct line_line_intersection
         // | pa pa |
         // | qb qb |
         auto const denominator_pq = determinant<line, &line::a, &line::b>(p, q);
-        constexpr decltype(denominator_pq) const zero = 0;
+        static decltype(denominator_pq) const zero = 0;
 
         if (equidistant)
         {

include/boost/geometry/strategies/cartesian/side_rounded_input.hpp

@@ -47,7 +47,7 @@ struct side_rounded_input
         coor_t const p_x = geometry::get<0>(p);
         coor_t const p_y = geometry::get<1>(p);
 
-        constexpr coor_t eps = std::numeric_limits<coor_t>::epsilon() / 2;
+        static coor_t const eps = std::numeric_limits<coor_t>::epsilon() / 2;
         coor_t const det = (p1_x - p_x) * (p2_y - p_y) - (p1_y - p_y) * (p2_x - p_x);
         coor_t const err_bound = (Coeff1 * eps + Coeff2 * eps * eps) *
             (  (geometry::math::abs(p1_x) + geometry::math::abs(p_x))