Using OPENSSL_SUPPRESS_DEPRECATED.

The macro is used to suppress deprecation warnings with OpenSSL 3.0.

Unlike OPENSSL_API_COMPAT, it works well with OpenSSL built with no-deprecated.
In particular, it doesn't unhide various macros in OpenSSL includes, which are
meant to be hidden under OPENSSL_NO_DEPRECATED.

src/nxt_openssl.c

@@ -6,6 +6,9 @@
 
 #include <nxt_main.h>
 #include <nxt_conf.h>
+
+#define OPENSSL_SUPPRESS_DEPRECATED
+
 #include <openssl/ssl.h>
 #include <openssl/conf.h>
 #include <openssl/err.h>