Make X509_REQ and X509_REQ_INFO opaque.

We can unexport the X509_REQ_INFO type entirely. (NB: OpenSSL hasn't
done this, but has unexported so much of X509_REQ_INFO that it is
impossible to use what remains anyway.)

Update-Note: Callers that reach into X509_REQ and X509_REQ_INFO must use
accessors instead.

Change-Id: I1eea5207b9195c8051d5e467acd63ad5f0caf89d
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/47564
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/crypto/x509/x_all.c b/crypto/x509/x_all.c
index a29e038..65347f9 100644
--- a/crypto/x509/x_all.c
+++ b/crypto/x509/x_all.c
@@ -66,6 +66,9 @@
 #include <openssl/rsa.h>
 #include <openssl/stack.h>
 
+#include "internal.h"
+
+
 int X509_verify(X509 *x509, EVP_PKEY *pkey)
 {
     if (X509_ALGOR_cmp(x509->sig_alg, x509->cert_info->signature)) {