Function call_exception_handler

extlibs/sol3/include/sol/sol.hpp:7436–7450

		}

		inline int call_exception_handler(lua_State* L, optional<const std::exception&> maybe_ex, string_view what) {
			lua_getglobal(L, default_exception_handler_name());
			type t = static_cast<type>(lua_type(L, -1));
			if (t != type::lightuserdata) {
				lua_pop(L, 1);
				return default_exception_handler(L, std::move(maybe_ex), std::move(what));
			}
			void* vfunc = lua_touserdata(L, -1);
			lua_pop(L, 1);
			if (vfunc == nullptr) {
				return default_exception_handler(L, std::move(maybe_ex), std::move(what));
			}
			exception_handler_function exfunc = reinterpret_cast<exception_handler_function>(vfunc);
			return exfunc(L, std::move(maybe_ex), std::move(what));
		}

#ifdef SOL_NO_EXCEPTIONS
		template <lua_CFunction f>