e_os.h removal from other headers and source files.

Removed e_os.h from all bar three headers (apps/apps.h crypto/bio/bio_lcl.h and
ssl/ssl_locl.h).

Added e_os.h into the files that need it now.

Directly reference internal/nelem.h when required.

Reviewed-by: Andy Polyakov <appro@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4188)
diff --git a/crypto/dsa/dsa_lib.c b/crypto/dsa/dsa_lib.c
index c90d09b..efd98c2 100644
--- a/crypto/dsa/dsa_lib.c
+++ b/crypto/dsa/dsa_lib.c
@@ -1,5 +1,5 @@
 /*
- * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 1995-2017 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the OpenSSL license (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
@@ -11,6 +11,7 @@
 
 #include <stdio.h>
 #include "internal/cryptlib.h"
+#include "e_os.h"
 #include <openssl/bn.h>
 #include "dsa_locl.h"
 #include <openssl/asn1.h>