Executes the command specified as a shell command.   The name of the system
command can be changed in tintin.h for your security.
#system {command} {option}
options: (default is 0)
option 1: add "> tintin.out", then show the contents of tintin.out in yTin screen (can be
actioned).
option 0: do not apprend " > tintin.out" to cmdline, default TinTin++ style. Under unix,
               this will show stdout, but will not be able to set action on the stdout.
Notice: if use some commands like vi, please DONOT use option {1}.
NEW from yTin1.82 (windows):
#system perl {script.pl}
This will try to call perl56.dll and will not show annoying DOS prompt.
Limit: NO stdin/stdout/stderr yet, but one can always let the perl script write to
a file, then use #sysecho to show on the screen, or #read/#textin to execute the
command.