printf format string validation is here

[kinke]

On Saturday, 22 February 2020 at 08:06:59 UTC, Walter Bright 
wrote:
> Is it time to throw old VS support under the bus?

I've been advocating that for years, due to the MSVC 2015 runtime 
finally featuring near-complete C99 standard compliance and thus 
vastly simplifying portability and rendering previous workarounds 
and test special cases in druntime/Phobos obsolete. LDC has been 
requiring MSVC 2015+ for years.

That said, Rainer went to great lengths to maintain support with 
pre-UCRT due to the ease of redistribution (bundling 1 DLL vs. 
potential UCRT Windows component installation), so dumping it now 
just because of `%z` seems excessive to me.