Fortify poll and ppoll.

And remove the test for FD_ZERO fortification, which never made much
sense anyway.

Change-Id: Id1009c5298d461fa4722189e8ecaf22f0c529536
diff --git a/libc/Android.mk b/libc/Android.mk
index 691017a..90f1a12 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -69,6 +69,7 @@
     bionic/__FD_chk.cpp \
     bionic/__fgets_chk.cpp \
     bionic/__memmove_chk.cpp \
+    bionic/__poll_chk.cpp \
     bionic/__read_chk.cpp \
     bionic/__recvfrom_chk.cpp \
     bionic/__stpcpy_chk.cpp \