ip: better --help

ip: better --help

Was:
    Usage: ip [OPTIONS] address|route|link|tunnel|neigh|rule [COMMAND]

    ip [OPTIONS] OBJECT [COMMAND]
    where OBJECT := address|route|link|tunnel|neigh|rule
    OPTIONS := -f[amily] inet|inet6|link | -o[neline]

User: instead of repeating list of OBJECTs twice, you could at least
show available COMMANDs...

Now:
    Usage: ip [OPTIONS] address|route|link|tunnel|neigh|rule [COMMAND]

    OPTIONS := -f[amily] inet|inet6|link | -o[neline]
    COMMAND :=
    ip addr add|del IFADDR dev IFACE | show|flush [dev IFACE] [to PREFIX]
    ip route list|flush|add|del|change|append|replace|test ROUTE
    ip link set IFACE [up|down] [arp on|off] | show [IFACE]
    ip tunnel add|change|del|show [NAME]
        [mode ipip|gre|sit]
        [remote ADDR] [local ADDR] [ttl TTL]
    ip neigh show|flush [to PREFIX] [dev DEV] [nud STATE]
    ip rule [list] | add|del SELECTOR ACTION

While at it, tweak tc --help too (it stays disabled, thus no effect)

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>