Concatenating mismatched string WORKS in VC2015 - How?

When we have either of these:

auto city1 = "New "  L"Delhi";
auto city2 = L"New " "York";

Any pre-VS2015 compiler would raise error:

error C2308: concatenating mismatched strings

But with VC2015 compiler, it compiles well and the resultant type (auto deduction) is a wide-char string.

My question is: When and How this is made possible - any standard specification?