Drop <sys/user.h> to fix PAGE_SIZE declaration

On some systems PAGE_SIZE is declared as sysconf(_SC_PAGESIZE) in <sys/user.h>
this is non-constant expression, so it cannot be used in type declarations.

This breaks compilation with a very non-obvious error message:

  CC       parasite-syscall.o
In file included from parasite-syscall.c:30:0:
./include/parasite.h:90:8: error: variably modified ‘fds’ at file scope

crtools doesn't uses anything from <sys/user.h>, so we can drop its usage.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-restore.c

@@ -14,7 +14,6 @@
 #include <sys/mman.h>
 #include <sys/vfs.h>
 #include <sys/ptrace.h>
-#include <sys/user.h>
 #include <sys/wait.h>
 #include <sys/file.h>
 #include <sys/shm.h>

parasite-syscall.c

@@ -11,7 +11,6 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <sys/mman.h>
-#include <sys/user.h>
 #include <sys/wait.h>
 #include <sys/socket.h>
 

test/zdtm/live/transition/fork.c

@@ -7,7 +7,6 @@
 #include <stdlib.h>
 #include <sys/wait.h>
 #include <sys/mman.h>
-#include <sys/user.h>
 #include <sys/types.h>
 #include <sys/syscall.h>
 

test/zdtm/live/transition/ptrace.c

@@ -7,7 +7,6 @@
 #include <stdlib.h>
 #include <sys/wait.h>
 #include <sys/mman.h>
-#include <sys/user.h>
 #include <sys/types.h>
 #include <sys/syscall.h>
 

util.c

@@ -25,7 +25,6 @@
 #include <sys/mman.h>
 #include <sys/vfs.h>
 #include <sys/ptrace.h>
-#include <sys/user.h>
 #include <sys/wait.h>
 #include <sys/resource.h>
 #include <sys/wait.h>