Add missing symbols to android-18 libc

This affects libc.so for android-18 and 19

Symbols missing from NDK libc but present in the
platform version of libc:

__strchr_chk
__strrchr_chk
__umask_chk
ffs # x86 only
getauxval
getdelim
getline
signalfd
wait4 # already present in android-19

Bug: http://b/28864994
Change-Id: Ib8ccc3706516be9590f2646edefac389d8538319
12 files changed