lsfd: print the detail of the timer associated with a timerfd

lsfd: print the detail of the timer associated with a timerfd

An example output:

    # ./lsfd -p 1  -Q '(TYPE == "timerfd")' -oCOMMAND,PID,ASSOC,TYPE,INODE,NAME
    COMMAND PID ASSOC    TYPE INODE NAME
    systemd   1    22 timerfd  1060 clockid=monotonic remaining=4625.661834645
    systemd   1    25 timerfd  1060 clockid=realtime remaining=398.164618943
    systemd   1   112 timerfd  1060 clockid=realtime remaining=7537606384.202715161

Added three new columns, TIMERFD.{CLOCKID,TIMERFD.REMAINING,INTERVAL}.
The filter engine works well with them.

An example listing timerfd files expiring within 1.2 seconds.

    # ./lsfd -Q '(TIMERFD.REMAINING > 0.0) && (TIMERFD.REMAINING < 1.2)'
    COMMAND          PID        USER ASSOC MODE    TYPE       SOURCE MNTID INODE NAME
    Xorg           17069         jet    26  rw- timerfd anon_inodefs    15  1060 clockid=monotonic remaining=0.061075544
    systemd-oomd 2382701 systemd-oom     8  rw- timerfd anon_inodefs    15  1060 clockid=monotonic remaining=0.178126915

Using SCOLS_JSON_NUMBER as the data type for TIMERFD.REMAINING and
TIMERFD.INTERVAL columns is suggested by Thomas Weißschuh
<thomas@t-8ch.de>.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>