socket: add own cross-platform declaration

Like with stdex::locale_t, this frees us from using Windowsizms on other
platforms. Sockets came from Unix to Windows and not the other way
around in the first place.

Signed-off-by: Simon Rozman <simon@rozman.si>

UnitTests/pch.hpp

@@ -19,6 +19,7 @@
 #include <stdex/progress.hpp>
 #include <stdex/ring.hpp>
 #include <stdex/sgml.hpp>
+#include <stdex/socket.hpp>
 #include <stdex/stream.hpp>
 #include <stdex/string.hpp>
 #include <stdex/sys_info.hpp>