Fix #include poll.h and sys/cdefs.h

POSIX defines poll.h, sys/poll.h should not be used at is c-library
internal header which may or may not exist. Notable in musl it
generates warning of being incorrect. And add explict include of
sys/cdefs.h where needed.

Change-Id: I142930df53fe7585a06b854b6faddc5301e024be