SSL_CTX_set_verify.pod: move a typedef in front of its first usage

Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1956)

doc/man3/SSL_CTX_set_verify.pod

@@ -12,6 +12,8 @@ SSL_verify_cb
 
  #include <openssl/ssl.h>
 
+ typedef int (*SSL_verify_cb)(int preverify_ok, X509_STORE_CTX *x509_ctx);
+
  void SSL_CTX_set_verify(SSL_CTX *ctx, int mode, SSL_verify_cb verify_callback);
  void SSL_set_verify(SSL *s, int mode, SSL_verify_cb verify_callback);
  SSL_get_ex_data_X509_STORE_CTX_idx(void);
@@ -19,9 +21,6 @@ SSL_verify_cb
  void SSL_CTX_set_verify_depth(SSL_CTX *ctx, int depth);
  void SSL_set_verify_depth(SSL *s, int depth);
 
-
- typedef int (*SSL_verify_cb)(int preverify_ok, X509_STORE_CTX *x509_ctx);
-
 =head1 DESCRIPTION
 
 SSL_CTX_set_verify() sets the verification flags for B<ctx> to be B<mode> and