udhcpc: new -x hostname:xxx option

[Maris, Rob]

Due to a busybox update I have changed my invocation of udhcpc for using  
-x hostname:<hostname> instead of -H <hostname>.
However, <hostname> is not recognized.

ps shows up: {busybox} udhcpc -x hostname -iwlan0
(the part with :<hostname> is missing)

However, I see that the behaviour seems comparable with other options.  
Apparently something else is wrong, supposedly in my configuration. What  
to do?

-Rob