Remove dependencies on obsolete __ARCH_WANT_SYSCALL_NO_FLAGS syscalls.

(aarch64 kernels only have the newer system calls.)

Also expose the new functionality that's exposed by glibc in our header files.

Change-Id: I45d2d168a03f88723d1f7fbf634701006a4843c5

libc/arch-x86/syscalls/dup3.S

@@ -0,0 +1,28 @@
+/* Generated by gensyscalls.py. Do not edit. */
+
+#include <asm/unistd.h>
+#include <linux/err.h>
+#include <machine/asm.h>
+
+ENTRY(dup3)
+    pushl   %ebx
+    pushl   %ecx
+    pushl   %edx
+    mov     16(%esp), %ebx
+    mov     20(%esp), %ecx
+    mov     24(%esp), %edx
+    movl    $__NR_dup3, %eax
+    int     $0x80
+    cmpl    $-MAX_ERRNO, %eax
+    jb      1f
+    negl    %eax
+    pushl   %eax
+    call    __set_errno
+    addl    $4, %esp
+    orl     $-1, %eax
+1:
+    popl    %edx
+    popl    %ecx
+    popl    %ebx
+    ret
+END(dup3)