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
diff --git a/libc/arch-arm/syscalls/dup3.S b/libc/arch-arm/syscalls/dup3.S
new file mode 100644
index 0000000..ad21254
--- /dev/null
+++ b/libc/arch-arm/syscalls/dup3.S
@@ -0,0 +1,16 @@
+/* Generated by gensyscalls.py. Do not edit. */
+
+#include <asm/unistd.h>
+#include <linux/err.h>
+#include <machine/asm.h>
+
+ENTRY(dup3)
+    mov     ip, r7
+    ldr     r7, =__NR_dup3
+    swi     #0
+    mov     r7, ip
+    cmn     r0, #(MAX_ERRNO + 1)
+    bxls    lr
+    neg     r0, r0
+    b       __set_errno
+END(dup3)