ITS#9348 don't declare sys_errlist if not present

If HAVE_SYS_ERRLIST is false, nothing uses them anyway, so the
declarations serve no purpose. Just breaks the compile if the
library actually defines them (and we are avoiding using them).

include/ac/errno.h

@@ -23,11 +23,7 @@
 # include <sys/errno.h>
 #endif
 
-#ifndef HAVE_SYS_ERRLIST
-	/* no sys_errlist */
-#	define		sys_nerr	0
-#	define		sys_errlist	((char **)0)
-#elif defined( DECL_SYS_ERRLIST )
+#if defined( HAVE_SYS_ERRLIST ) && defined( DECL_SYS_ERRLIST )
 	/* have sys_errlist but need declaration */
 	LDAP_LIBC_V(int)      sys_nerr;
 	LDAP_LIBC_V(char)    *sys_errlist[];