Get rid of warning on platforms for casting char -> int

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/init.c b/init.c
index baf3130..4e7eb49 100644
--- a/init.c
+++ b/init.c
@@ -776,7 +776,7 @@
 			return 1;
 		if (line[i] == '#')
 			return 1;
-		if (!isspace(line[i]) && !iscntrl(line[i]))
+		if (!isspace((int) line[i]) && !iscntrl((int) line[i]))
 			return 0;
 	}