android: remove syscalls implemented in libbb

We missed the addition of libbb/missing_syscalls.c in 1.21

This also fix 'busybox date -s "2014-08-06 14:15:15"'
(tested in recovery too)

Change-Id: I2a1297e894638f000734b15757100c2d48984ed3
Android.mk: toggle l-preview config flag

Change-Id: I4465b88a0337f5f267d501a94b2f71f8ef07b318
Test some tty related applets (getty, login, su)

and passwd, mkpasswd, cryptpw

Change-Id: I96ee64f0872856fad6b3ff299faafad6451da556