ripd: fix compiler warnings

ripd: fix compiler warnings

* ripd/rip_interface.c
  * rip_request_neighbor(): comment out, unused
  * rip_request_neighbor_all(): idem
  * rip_interface_up(): Cast flags otherwise compiler complains
    about %lld not matching uint64_t on 64 bit x86. Print in hex
    since flags are bit field.
  * rip_interface_add(): idem
  * rip_interface_delete(): idem
* ripd/rip_zebra.c
  * rip_redistribute_set(): comment out, unused
* ripd/ripd.h
  * rip_redistribute_check(): move prototype here so compiler
    can check function against prototype
* ripd/ripd.c
  * rip_update_default_metric(): comment out, unused