DIP1000 finds stack corruption bug in std.socket

[Walter Bright]

https://github.com/dlang/phobos/pull/6919

The function returns a pointer to a local variable. The pre-DIP1000 code 
circumvented the compiler error message by passing the address through another 
variable. DIP1000 tracks the lifetimes across assignments, exposing such 
shenanigans.

These sorts of bugs can be very hard to track down by their effects.