Revert "Lose the hand-written futex assembler."

This reverts commit ced906c849704f379d7191822f6d74993d4fa296.

Causes issues on art / dalvik due to a broken return value
check and other undiagnosed issues.

bug: 15195455

Change-Id: I5d6bbb389ecefb0e33a5237421a9d56d32a9317c
diff --git a/libc/arch-x86/syscalls/futex.S b/libc/arch-x86/syscalls/futex.S
new file mode 100644
index 0000000..7a52913
--- /dev/null
+++ b/libc/arch-x86/syscalls/futex.S
@@ -0,0 +1,42 @@
+/* Generated by gensyscalls.py. Do not edit. */
+
+#include <private/bionic_asm.h>
+
+ENTRY(futex)
+    pushl   %ebx
+    pushl   %ecx
+    pushl   %edx
+    pushl   %esi
+    pushl   %edi
+    pushl   %ebp
+    .cfi_def_cfa_offset 24
+    .cfi_rel_offset ebx, 0
+    .cfi_rel_offset ecx, 4
+    .cfi_rel_offset edx, 8
+    .cfi_rel_offset esi, 12
+    .cfi_rel_offset edi, 16
+    .cfi_rel_offset ebp, 20
+    mov     28(%esp), %ebx
+    mov     32(%esp), %ecx
+    mov     36(%esp), %edx
+    mov     40(%esp), %esi
+    mov     44(%esp), %edi
+    mov     48(%esp), %ebp
+    movl    $__NR_futex, %eax
+    int     $0x80
+    cmpl    $-MAX_ERRNO, %eax
+    jb      1f
+    negl    %eax
+    pushl   %eax
+    call    __set_errno
+    addl    $4, %esp
+    orl     $-1, %eax
+1:
+    popl    %ebp
+    popl    %edi
+    popl    %esi
+    popl    %edx
+    popl    %ecx
+    popl    %ebx
+    ret
+END(futex)