LibC: Add missing sys/cdefs.h include

Some header files use __BEGIN_DECLS without including sys/cdefs.h.
This causes issues for C code that compiles against these headers,
which may occur with Ports.

Userland/Libraries/LibC/sys/mman.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <Kernel/API/POSIX/sys/mman.h>
+#include <sys/cdefs.h>
 
 __BEGIN_DECLS
 

Userland/Libraries/LibC/sys/ptrace.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <Kernel/API/POSIX/sys/ptrace.h>
+#include <sys/cdefs.h>
 
 __BEGIN_DECLS
 

Userland/Libraries/LibC/sys/socket.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <Kernel/API/POSIX/sys/socket.h>
+#include <sys/cdefs.h>
 #include <sys/un.h>
 
 __BEGIN_DECLS

Userland/Libraries/LibC/sys/statvfs.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <Kernel/API/POSIX/sys/statvfs.h>
+#include <sys/cdefs.h>
 
 __BEGIN_DECLS
 

Userland/Libraries/LibC/sys/time.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <Kernel/API/POSIX/sys/time.h>
+#include <sys/cdefs.h>
 #include <time.h>
 
 __BEGIN_DECLS

Userland/Libraries/LibC/sys/times.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <Kernel/API/POSIX/sys/times.h>
+#include <sys/cdefs.h>
 
 __BEGIN_DECLS
 

Userland/Libraries/LibC/sys/uio.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <Kernel/API/POSIX/sys/uio.h>
+#include <sys/cdefs.h>
 
 __BEGIN_DECLS
 

Userland/Libraries/LibC/sys/utsname.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <Kernel/API/POSIX/sys/utsname.h>
+#include <sys/cdefs.h>
 
 __BEGIN_DECLS
 

Userland/Libraries/LibC/sys/wait.h

@@ -8,6 +8,7 @@
 
 #include <Kernel/API/POSIX/signal.h>
 #include <Kernel/API/POSIX/sys/wait.h>
+#include <sys/cdefs.h>
 
 __BEGIN_DECLS
 

Userland/Libraries/LibC/sys/xattr.h

@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <sys/cdefs.h>
 #include <sys/types.h>
 
 __BEGIN_DECLS