adding 'mark' support in u32 filter

[Sagi Lowenhardt]

Hi
I've implemented support to filter by 'mark' and it seems to work fine 
but with 2 workarounds.
1. I have to set the filter as 'terminate', although it should be set 
automatically as I set 'flowid' (by to the code in f_u32.c in 
'iproute'), otherwise the filter shown with asterisk and the filter 
does nothing.
2. I have to set selector, even with all values set to 0, otherwise I 
get errno 7-'Invalid input data or parameter' as I try to add the 
filter to TC.

Of course I'll send the patch as I complete the implementation, but I 
was wondering if these 2 workarounds can be eliminated somehow.

Thanks