Anywhere but the beam sources we shouldn't #include "erl_nif.h", because
what "erl_nif.h" does is: (1) fail to find it outside of -I dirs, (2)
then treat it as if it was written like <erl_nif.h>. Using <erl_nif.h>
skips (1).

More information can be found in 6.10.2 of the C standard.

Because the examples use "erl_nif.h", NIF projects in the Erlang
ecosystem copy this verbatim and make the same mistake.

This only produces an error on win32, but should not really be called
on *nix either.

The sha of the original change is 52810718b