Add accept4() syscall

Add accept4() using SYSCALLS.TXT and gensyscall

Change-Id: I6f19f29144186d15d46423e10f2cc4b4223719c6
diff --git a/libc/arch-x86/syscalls/accept4.S b/libc/arch-x86/syscalls/accept4.S
new file mode 100644
index 0000000..dc3c1f5
--- /dev/null
+++ b/libc/arch-x86/syscalls/accept4.S
@@ -0,0 +1,27 @@
+/* Generated by gensyscalls.py. Do not edit. */
+
+#include <private/bionic_asm.h>
+
+ENTRY(accept4)
+    pushl   %ebx
+    pushl   %ecx
+    .cfi_def_cfa_offset 8
+    .cfi_rel_offset ebx, 0
+    .cfi_rel_offset ecx, 4
+    mov     $18, %ebx
+    mov     %esp, %ecx
+    addl    $12, %ecx
+    movl    $__NR_socketcall, %eax
+    int     $0x80
+    cmpl    $-MAX_ERRNO, %eax
+    jb      1f
+    negl    %eax
+    pushl   %eax
+    call    __set_errno
+    addl    $4, %esp
+    orl     $-1, %eax
+1:
+    popl    %ecx
+    popl    %ebx
+    ret
+END(accept4)