[RFE] AIX support

[bmarwell]

Hi,

The library is crossplatform and has both terminal-based implementations on *nix operating systems

Sadly, it does not compile on AIX. I tried gotop:

GOOS=aix GOARCH=ppc64 go build -C cmd/gotop -trimpath -ldflags="-s -w " -o tree.aix.ppc64-nodebug

However, it does not compile with:

❯ GOOS=aix GOARCH=ppc64 go build -C cmd/gotop  -trimpath -ldflags="-s -w "  -o tree.aix.ppc64-nodebug
# github.com/distatus/battery
../../../../go/pkg/mod/github.com/distatus/battery@v0.10.0/battery.go:118:13: undefined: systemGet
../../../../go/pkg/mod/github.com/distatus/battery@v0.10.0/battery.go:155:16: undefined: systemGetAll
# github.com/nsf/termbox-go
../../../../go/pkg/mod/github.com/nsf/termbox-go@v0.0.0-20200418040025-38ba6e5628f1/termbox.go:58:17: undefined: syscall_Termios
../../../../go/pkg/mod/github.com/nsf/termbox-go@v0.0.0-20200418040025-38ba6e5628f1/termbox.go:277:37: undefined: syscall_Termios
../../../../go/pkg/mod/github.com/nsf/termbox-go@v0.0.0-20200418040025-38ba6e5628f1/termbox.go:286:37: undefined: syscall_Termios
../../../../go/pkg/mod/github.com/nsf/termbox-go@v0.0.0-20200418040025-38ba6e5628f1/api.go:55:46: undefined: syscall.O_ASYNC
../../../../go/pkg/mod/github.com/nsf/termbox-go@v0.0.0-20200418040025-38ba6e5628f1/api.go:69:17: undefined: syscall_IGNBRK
../../../../go/pkg/mod/github.com/nsf/termbox-go@v0.0.0-20200418040025-38ba6e5628f1/api.go:69:34: undefined: syscall_BRKINT
../../../../go/pkg/mod/github.com/nsf/termbox-go@v0.0.0-20200418040025-38ba6e5628f1/api.go:69:51: undefined: syscall_PARMRK
../../../../go/pkg/mod/github.com/nsf/termbox-go@v0.0.0-20200418040025-38ba6e5628f1/api.go:70:3: undefined: syscall_ISTRIP
../../../../go/pkg/mod/github.com/nsf/termbox-go@v0.0.0-20200418040025-38ba6e5628f1/api.go:70:20: undefined: syscall_INLCR
../../../../go/pkg/mod/github.com/nsf/termbox-go@v0.0.0-20200418040025-38ba6e5628f1/api.go:70:36: undefined: syscall_IGNCR
../../../../go/pkg/mod/github.com/nsf/termbox-go@v0.0.0-20200418040025-38ba6e5628f1/api.go:70:36: too many errors

AIX has way different syscalls it seems and is a "proper" UNIX.