Check getline()-return-values properly

It's not useful when 0 is returned anyway, so be sure that we have a
string with length > 0, this also solves some indexing-gotchas like
"len - 1" and so on.
Also, add checked getline()'s whenever it has been forgotten and
clean up the error-messages.

cron.c

@@ -304,7 +304,7 @@ loadentries(void)
 		return -1;
 	}
 
-	for (y = 0; (len = getline(&line, &size, fp)) != -1; y++) {
+	for (y = 0; (len = getline(&line, &size, fp)) > 0; y++) {
 		p = line;
 		if (line[0] == '#' || line[0] == '\n' || line[0] == '\0')
 			continue;