Math: fix Range compilation with Clang, mark the constructors as implicit.
Math: fix Range compilation with Clang, mark the constructors as implicit.

Somehow defaulted constructor is not enough and Clang complained about
no user-provided default constructor.

MiUishadow/magnum,MiUishadow/magnum,ashimidashajia/magnum,MiUishadow/magnum,MiUishadow/magnum,MiUishadow/magnum,ashimidashajia/magnum,DerThorsten/magnum,DerThorsten/magnum,DerThorsten/magnum,ashimidashajia/magnum,DerThorsten/magnum,ashimidashajia/magnum,ashimidashajia/magnum,MiUishadow/magnum,DerThorsten/magnum