If we send a process to foreground while the headless instance may get
a SIGTTOU/SIGTTIN, if not ignored this signal will stop the headless.
It's not clear why this only happens the second time we do this but
that's how it is.
Also removes the direct syscall to TIOCSPGRP and lets the go runtime do
it instead.
Fixes#1279
Change the linux verison of proc/native and proc/gdbserial (with
debugserver) so that they let the target process use the terminal when
delve is launched in headless mode.
Windows already worked, proc/gdbserial (with rr) already worked.
I couldn't find a way to make proc/gdbserial (with lldb-server) work.
No tests are added because I can't think of a way to test for
foregroundness of a process.
Fixes#65
