Do not lazily use BUFSIZ for "I don't care what size" when building

strings because it is only guaranteed to be 256 bytes and even the
default 1024 is not always enough. Reported by Gregory Pakosz.

cmd.c

@@ -384,7 +384,7 @@ cmd_find(const char *name, char **cause)
 {
 	const struct cmd_entry	**loop, *entry, *found = NULL;
 	int			  ambiguous;
-	char			  s[BUFSIZ];
+	char			  s[8192];
 
 	ambiguous = 0;
 	for (loop = cmd_table; *loop != NULL; loop++) {