Revert "Replaces vfork() implementation with fork()"

We're getting cold feet on this one... let's put it back.

This reverts commit 210331d9762037afb9b5ed8413079c6f65872df9.

Change-Id: I6b0d3c2b1dbf7f1dc9566979a91b7504c2189269
diff --git a/libc/arch-arm/syscalls/vfork.S b/libc/arch-arm/syscalls/vfork.S
new file mode 100644
index 0000000..e12fba5
--- /dev/null
+++ b/libc/arch-arm/syscalls/vfork.S
@@ -0,0 +1,14 @@
+/* Generated by gensyscalls.py. Do not edit. */
+
+#include <private/bionic_asm.h>
+
+ENTRY(vfork)
+    mov     ip, r7
+    ldr     r7, =__NR_vfork
+    swi     #0
+    mov     r7, ip
+    cmn     r0, #(MAX_ERRNO + 1)
+    bxls    lr
+    neg     r0, r0
+    b       __set_errno
+END(vfork)