SSL: include correct OpenSSL headers.

Previously, <bn.h>, <dh.h>, <rand.h> and <rsa.h> were pulled in
by <engine.h> using OpenSSL's deprecated interface, which meant
that nginx couldn't have been built with -DOPENSSL_NO_DEPRECATED.

Both <x509.h> and <x509v3.h> are pulled in by <ocsp.h>, but we're
calling X509 functions directly, so let's include those as well.

<crypto.h> is pulled in by virtually everything, but we're calling
CRYPTO_add() directly, so let's include it as well.

Signed-off-by: Piotr Sikora <piotr@cloudflare.com>

src/event/ngx_event_openssl.h

diff --git a/src/event/ngx_event_openssl.h b/src/event/ngx_event_openssl.h
index 0194602..174c865 100644
--- a/src/event/ngx_event_openssl.h
+++ b/src/event/ngx_event_openssl.h
@@ -14,10 +14,17 @@
 
 #include <openssl/ssl.h>
 #include <openssl/err.h>
+#include <openssl/bn.h>
 #include <openssl/conf.h>
+#include <openssl/crypto.h>
+#include <openssl/dh.h>
 #include <openssl/engine.h>
 #include <openssl/evp.h>
 #include <openssl/ocsp.h>
+#include <openssl/rand.h>
+#include <openssl/rsa.h>
+#include <openssl/x509.h>
+#include <openssl/x509v3.h>
 
 #define NGX_SSL_NAME     "OpenSSL"