U32 classifier and new hashing support

[A C]

I recently pulled the git tree and saw the new u32 hashing support and
had a quick question about it.  Is there a reason
rtnl_u32_set_hashmask/rtnl_u32_set_cls_terminal are adding new keys to
the selector?  I don't quite understand why rtnl_u32_set_cls_terminal
needs to be different than rtnl_u32_set_flags(..., TC_U32_TERMINAL).

On a side note, perhaps it would useful to include a note about the
importance of TC_U32_TERMINAL in the docs for u32 classid?  For the
most part, the docs specify everything needed to get a filter up and
working, but it was non-obvious to me without looking at
iproute2/kernel that this flag is required for the classid to go
anywhere.