Revert "fix REQ-42"

This reverts commit 4a0682bbc1.

The reverted commit appears to be wrong, for example:
- arch_range_check()'s arguments and parameters are mismatch.
- arch_range_check() implementation is not checking range.

Conflicts:
	kernel/syscall.c

arch/x86/kernel/syscall.c

@@ -1278,18 +1278,6 @@ set_signal(int sig, void *regs0, siginfo_t *info)
 		do_kill(thread, thread->proc->pid, thread->tid, sig, info, 0);
 }
 
-int
-arch_range_check(unsigned long addr)
-{
-	struct thread *thread = cpu_local_var(current);
-	struct vm_regions *region = &thread->vm->region;
-
-	if(addr < region->user_start ||
-	   addr > region->user_end)
-		return -EINVAL;
-	return 0;
-}
-
 SYSCALL_DECLARE(mmap)
 {
 	const int supported_flags = 0