Remove #include <sys/cdefs.h>

These are not provided by standards, and as a result causes failure to
compile on musl.

https://wiki.musl-libc.org/faq.html#Q:-When-compiling-something-against-musl,-I-get-error-messages-about-%3Ccode%3Esys/cdefs.h%3C/code%3E

Change-Id: I6a357cefd106c72cfecafd898638f6b5692c2e05

main/ast_expr2.c

@@ -94,7 +94,6 @@
 #define ASTMM_LIBC ASTMM_REDIRECT
 #include "asterisk.h"
 
-#include <sys/cdefs.h>
 #include <sys/types.h>
 #include <stdio.h>
 

main/ast_expr2.y

@@ -15,7 +15,6 @@
 #define ASTMM_LIBC ASTMM_REDIRECT
 #include "asterisk.h"
 
-#include <sys/cdefs.h>
 #include <sys/types.h>
 #include <stdio.h>
 

utils/db1-ast/include/db.h

@@ -37,7 +37,6 @@
 #define	_DB_H 1
 
 #include <sys/types.h>
-#include <sys/cdefs.h>
 
 #include <limits.h>