bio/bss_log.c: on DJGPP syslog facility is part of sockets library.

In other words no-sock DJGPP build should suppress syslogging.
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5708)

crypto/bio/bss_log.c

@@ -39,6 +39,8 @@ void *_malloc32(__size_t);
 #  endif                        /* __INITIAL_POINTER_SIZE == 64 */
 # endif                         /* __INITIAL_POINTER_SIZE && defined
                                  * _ANSI_C_SOURCE */
+#elif defined(__DJGPP__) && defined(OPENSSL_NO_SOCK)
+# define NO_SYSLOG
 #elif (!defined(MSDOS) || defined(WATT32)) && !defined(OPENSSL_SYS_VXWORKS) && !defined(NO_SYSLOG)
 # include <syslog.h>
 #endif