script: add more info to script header

script: add more info to script header

This patch introduces [...] to store extra information about terminal
to the typescript header. For example:

  Script started on 2018-05-14 12:52:32+02:00 [TERM="xterm-256color" TTY="/dev/pts/3" COLS="190" LINES="53"]

or

  Script started on 2018-05-14 12:54:01+02:00 [<not executed on terminal>]

if stdout is not terminal.

Addresses: https://github.com/karelzak/util-linux/issues/583
Signed-off-by: Karel Zak <kzak@redhat.com>