This commit adds support for AIX operating system.
- move term_solaris.go to term_nosyscall6.go. AIX like solaris doesn't
provide syscall.Syscall6 and must rely on x/sys/unix in order to perform
syscalls.
- This patch won't work with versions prior to 1.13 because it needs
some constants added by https://go-review.googlesource.com/c/go/+/171339.
Clément Chigot