Return `void*` from _d_allocclass so LLVM doesn't do weird things with it... This allows `-instcombine` followed by `-gvn` to do devirtualization, so add `-gvn` in strategic places in the default pass order.

import tango.io.Stdout;

void main()
{
    Stdout("Hello World").newline;
    Stdout.formatln("{} {}", "Hello", "World");
}