perlfc.pl: Introduce open_command

Introduce an open_command, which can be used to send
a command to crash, instead of duplicating each step
everywhere.

Signed-off-by: Vinayak Menon <vinayakm.list@gmail.com>
extscript: fix coding style errors

Signed-off-by: Vinayak Menon <vinayakm.list@gmail.com>
perlfc: add vmallocinfo command

Signed-off-by: Vinayak Menon <vinayakm.list@gmail.com>
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>
extscript: unlink the socket in unbind.

And a minor change in perlfc.pl. The error
message on command failure is edited.

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