udhcp: dname_dec may return NULL, account for that case

Other random cleanips included...

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/networking/udhcp/options.h b/networking/udhcp/options.h
index 8c80485..9e62431 100644
--- a/networking/udhcp/options.h
+++ b/networking/udhcp/options.h
@@ -19,11 +19,13 @@
 	OPTION_U16,
 	OPTION_S16,
 	OPTION_U32,
-	OPTION_S32
+	OPTION_S32,
 };
 
-#define OPTION_REQ      0x10 /* have the client request this option */
-#define OPTION_LIST     0x20 /* There can be a list of 1 or more of these */
+/* Client requests this option by default */
+#define OPTION_REQ      0x10
+/* There can be a list of 1 or more of these */
+#define OPTION_LIST     0x20
 
 /*****************************************************************/
 /* Do not modify below here unless you know what you are doing!! */