Use rvalue ref for arguments that are destroyed

[mglisse]

/! Builds an alpha shape of mode m from the triangulation dt. \attention This operation destroys the triangulation dt. / Alpha_shape_3(Dt& dt, FT alpha = 0, Mode m = REGULARIZED);

Since C++11, it would seem more natural to make the first argument Dt&& dt. Of course, that would break some code, although it is easy enough to add std::move. The most inconvenient part is for users that must support multiple versions of CGAL, because I don't know how to write code that works with both, without a macro to actually have different code for both.

[lrineau]

Could we add an overload?

Alpha_shape_3(Dt& dt, FT alpha = 0, Mode m = REGULARIZED);
Alpha_shape_3(Dt&& dt, FT alpha = 0, Mode m = REGULARIZED);

[mglisse]

Makes sense (and possibly deprecate the old one at some point).