Deprecation: std.exception.enforceEx

[Samael]

In the same was as buggins/hibernated#60 this project should use the following to allow dmd versions above and below 2.089

// For backwards compatibily
// 'enforceEx' will be removed with 2.089
static if(__VERSION__ < 2080) {
    alias enforceHelper = enforceEx;
} else {
    alias enforceHelper = enforce;
}