[PATCH] Windows port: add support to setenv function

According to [1]/messages/by-id/29478.1576537771@sss.pgh.pa.us </messages/by-id/29478.1576537771@sss.pgh.pa.us&gt;, windows does not support setenv.
With the possibility of setenv going further [2]/messages/by-id/30119.1576538578@sss.pgh.pa.us </messages/by-id/30119.1576538578@sss.pgh.pa.us&gt;, I am submitting in this
thread, the patch to add setenv support on the windows side,
It is based on pre-existing functions, and seeks to correctly emulate the
functioning of the POSIX setenv, but has not yet been tested.
regards,

Ranier Vilela

[1]: /messages/by-id/29478.1576537771@sss.pgh.pa.us </messages/by-id/29478.1576537771@sss.pgh.pa.us&gt;
</messages/by-id/29478.1576537771@sss.pgh.pa.us&gt;
[2]: /messages/by-id/30119.1576538578@sss.pgh.pa.us </messages/by-id/30119.1576538578@sss.pgh.pa.us&gt;
</messages/by-id/30119.1576538578@sss.pgh.pa.us&gt;