Interrupt process PROCESS.
PROCESS may be a process, a buffer, or the name of a process or buffer.
No arg or nil means current buffer's process.
Second arg CURRENT-GROUP non-nil means send signal to
the current process-group of the process's controlling terminal
rather than to the process's own process group.
If the process is a shell, this means interrupt current subjob
rather than the shell.
If CURRENT-GROUP is `lambda', and if the shell owns the terminal,
don't send the signal. (fn &optional PROCESS CURRENT-GROUP)