(Re)move some things from e_os.h

Remove GETPID_IS_MEANINGLESS and osslargused.

Move socket-related things to new file internal/sockets.h; this is now
only needed by four(!!!) files.  Compiles should be a bit faster.
Remove USE_SOCKETS ifdef's

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4209)
diff --git a/test/handshake_helper.c b/test/handshake_helper.c
index 322957a..473e22d 100644
--- a/test/handshake_helper.c
+++ b/test/handshake_helper.c
@@ -16,11 +16,7 @@
 #include <openssl/srp.h>
 #endif
 
-#ifndef OPENSSL_NO_SOCK
-# define USE_SOCKETS
-# include "internal/nelem.h"
-#endif
-
+#include "internal/nelem.h"
 #include "handshake_helper.h"
 #include "testutil.h"