Use the same retain implementation for Win32 targets

Currently plc_Win32_main_retain.c is exact copy of
plc_Linux_main_retain.c, because it's not possible to use symbol
links.

It'd be nice in the future to have possibility to modify targets.code.

<?xml version="1.0" encoding="UTF-8"?>
<BeremizRoot URI_location="LOCAL://">
  <TargetType/>
</BeremizRoot>