Transitioning std lib modules/packages

[Andrea Fontana via Digitalmars-d]

On Monday, 28 November 2016 at 14:09:10 UTC, Ilya Yaroshenko 
wrote:
>> Instead of "API_LEVEL_DMD_*" this already works:
>>
>> static if (__VERSION__ >= 2072)
>
> Compiler version should be split from a library versions. --Ilya

But I can't set from compiler command line, I think. Something 
like:

dmd my_old_source.d -version=PHOBOS_API_LEVEL_2

And I think that inside phobos source a lot of breaking changes 
simply override old code and checking __VERSION__ is not useful 
at all. Am I wrong?