fix wrong version number 2.069 to 2.070

[alphaKAI]

I found that latest version of dmd's version remain 2.069, I fixed it to be 2.070.

[PetarKirov]

Since DMD 2.070 is already released, I think this should be now DMD 2.071, so we don't forget to change it for the next release.

[Geod24]

Or maybe we could generate it from the git tag so it doesn't have to be manually handled.

[WalterBright]

Who'd a-thunk that pulling this would break everything? Fix:

#5378

[tsbockman]

Since DMD 2.070 is already released, I think this should be now DMD 2.071, so we don't forget to change it for the next release.

This would also solve a problem I have, which is that __VERSION__ doesn't currently allow me to differentiate between HEAD and the last stable release.

[JackStouffer]

Who'd a-thunk that pulling this would break everything?

Auto tester is love. Auto tester is life.

[WebDrake]

Since DMD 2.070 is already released

... shouldn't this patch (and Walter's in #5378) nevertheless be applied to stable, and a v2.070.1 released with these corrections? As it is, phobos v2.0.70.0 is still building a libphobos2.so.0.69.

Happy to submit the PR, just wanted to check if there was any reason stable hadn't already been patched.