Move SS_CANTRCVMORE and SS_RCVATMARK bits from `so_state' to `sb_state' of

Move SS_CANTRCVMORE and SS_RCVATMARK bits from `so_state' to `sb_state' of
receive buffer. As it was done for SS_CANTSENDMORE bit, the definition
kept as is, but now these bits belongs to the `sb_state' of receive
buffer. `sb_state' ored with `so_state' when socket data exporting to the
userland.

ok bluhm@