android: backport pty implementation from aosp/master

This is not (yet) in l-preview branch but on master
The only way to prevent duplicated includes was to
test the existence of a new constant added after
l-preview bionic source release.

Also use compatible hasmntopt() return type
(swapon/off compilation warnings)

Signed-off-by: Tanguy Pruvot <tanguy.pruvot@gmail.com>

Change-Id: I4ee6e7752eab84de4566ae86a90171b8241fcaea
Fix remaining bionic warnings

Tested on arm and x86 (kitkat),
aosp/master has some other ones

Also update the readme and android.h

Change-Id: I170b16f2e091b99f971fb518bf0106c0e92adfdd
android: on prepare, clean all intermediates

This was requested to me to prevent no clobbered builds failures
on busybox config changes.

Change-Id: I1bdf2948e0669b1de567381eb809f576e8f1eef5
mktemp: include libc mktemp, safe in busybox

This commit remove the last warning in busybox,
and prevent users to try to use mkstemp which has not
the right behavior.

Change-Id: I5aaae8044769bb1893f2430287d72b3abbee796c
Android.mk: prevent warnings on make prepare

Add "+" to allow a new job

touch import_includes to prevent problems with -jN

Change-Id: Iea3cd527842a8bd770ff56fce01bcd0ff2d0db83
selinux: implement missing selinux functions

checkPasswdAccess() is deprecated
http://linux.die.net/man/3/selinux_check_passwd_access

also, ensure context is initialized in run_shell()

Note: these stubs are just compatible with busybox source code
Should be enhanced, or implemented in libselinux...

Change-Id: I22ea2679191d5c0887b6ef8c77f09a032c226876
Android: update busybox def PATH and cron folder

remove /usr/bin, add /vendor/bin, like official path

config folder was badly set to debian style cron.d
but busybox variant is a bit different :

  mkdir /etc/crontabs
  echo "* * * * * log CRON!" > /etc/crontabs/`whoami`
  crond -f

Change-Id: I0b9af08a557a952b5074da3231f32433f447f558
android: clearenv should not set environ to NULL

Remove the old internal clearenv() function which is
no more required (exported in libc)

Change-Id: I357f6a3b057c366761b481c09b471d7c53d7a419
Test some tty related applets (getty, login, su)

And passwd, mkpasswd, cryptpw

Sample /etc/passwd required before 'passwd' :
root:x:0:0:root:/:/system/xbin/bash

busybox su allow to change current user, if you are root
Example : "busybox su shell -c /system/xbin/bash"

busybox su is not symlinked to prevent problems with
the optional su daemon

getpwXXX() return now an empty string instead of null,
busybox often check directly pw->pw_passwd[0]

PS: This commit was made to test applets on bionic,
and will not be merged as-is later (new applets)

I will extract some changes in a separate commit

Change-Id: I96ee64f0872856fad6b3ff299faafad6451da556
selinux: fix for kitkat 4.2