Write POD page.

Reviewed-by: NRichard Levitte <levitte@openssl.org>

doc/ssl/SSL_SESSION_get_hostname.pod

+=pod
+
+=head1 NAME
+
+SSL_SESSION_get0_hostname - retrieve the SNI hostname associated with a session
+
+=head1 SYNOPSIS
+
+ #include <openssl/ssl.h>
+
+ const char *SSL_SESSION_get0_hostname(const SSL_SESSSION *s);
+
+=head1 DESCRIPTION
+
+SSL_SESSION_get0_hostname() retrieves the SNI value that was sent by the
+client when the session was created, or NULL if no value was sent.
+
+The value returned is a pointer to memory maintained within B<s> and
+should not be free'd.
+
+=head1 SEE ALSO
+
+L<ssl(3)>,
+L<d2i_SSL_SESSION(3)>,
+L<SSL_SESSION_get_time(3)>,
+L<SSL_SESSION_free(3)>
+
+=cut