env: Hide '.' variables in env print by default

When printing all variables with env print, don't print variables that
begin with '.'.  If env print is called with a '-a' switch, then
include variables that begin with '.' (just like the ls command).

Variables printed explicitly will be printed even without the -a.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>

common/env_dataflash.c

@@ -60,7 +60,7 @@ int saveenv(void)
 	char	*res;
 
 	res = (char *)&env_new.data;
-	len = hexport_r(&env_htab, '\0', &res, ENV_SIZE, 0, NULL);
+	len = hexport_r(&env_htab, '\0', 0, &res, ENV_SIZE, 0, NULL);
 	if (len < 0) {
 		error("Cannot export environment: errno = %d\n", errno);
 		return 1;