Make DSO opaque.

This was really easy.

Reviewed-by: Tim Hudson <tjh@openssl.org>

crypto/dso/dso_lib.c

diff --git a/crypto/dso/dso_lib.c b/crypto/dso/dso_lib.c
index 3082545..f464fab 100644
--- a/crypto/dso/dso_lib.c
+++ b/crypto/dso/dso_lib.c
@@ -56,10 +56,7 @@
  *
  */
 
-#include <stdio.h>
-#include <openssl/crypto.h>
-#include "internal/cryptlib.h"
-#include <openssl/dso.h>
+#include "dso_locl.h"
 
 static DSO_METHOD *default_DSO_meth = NULL;