Improve documentation, change copyright year, and remove redundant code.

Signed-off-by: Vinayak Menon <vinayakm.list@gmail.com>
extscript: Fix a race in closing command.out

close command.out only after the script exists.
And copy the saved jump buff as soon as exec_command
returns.

Signed-off-by: Vinayak Menon <vinayakm.list@gmail.com>