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

include/asterisk/compat.h

@@ -68,7 +68,7 @@
 #endif
 
 #ifndef AST_POLL_COMPAT
-#include <sys/poll.h>
+#include <poll.h>
 #else
 #include "asterisk/poll-compat.h"
 #endif

include/asterisk/poll-compat.h

@@ -83,7 +83,7 @@
 
 #ifndef AST_POLL_COMPAT
 
-#include <sys/poll.h>
+#include <poll.h>
 
 #define ast_poll(a, b, c) poll(a, b, c)
 

main/ast_expr2.c

@@ -93,6 +93,7 @@
 
 #include "asterisk.h"
 
+#include <sys/cdefs.h>
 #include <sys/types.h>
 #include <stdio.h>
 

main/ast_expr2.y

@@ -14,6 +14,7 @@
 
 #include "asterisk.h"
 
+#include <sys/cdefs.h>
 #include <sys/types.h>
 #include <stdio.h>