Add unshare() syscall.

(cherry-pick of 5467f25f82934d611c60f8bc57a05114f3c1bea0.)

Bug: 6925012
Change-Id: Ic5ea2fbd606311087de05d7a3594df2fa9b2fef9
diff --git a/libc/SYSCALLS.TXT b/libc/SYSCALLS.TXT
index 504a050..8f78e7f 100644
--- a/libc/SYSCALLS.TXT
+++ b/libc/SYSCALLS.TXT
@@ -1,6 +1,6 @@
 # this file is used to list all the syscalls that will be supported by
 # the Bionic C library. It is used to automatically generate the syscall
-# stubs, the list of syscall constants (__NR_xxxx) and the content of <linux/_unitsd.h>
+# stubs, the list of syscall constants (__NR_xxxx) and the content of <linux/_unistd.h>
 #
 # each non comment line has the following format:
 #
@@ -191,6 +191,7 @@
 int     removexattr(const char *, const char *) 235,235,233
 int     lremovexattr(const char *, const char *) 236,236,234
 int     __statfs64:statfs64(const char *, size_t, struct statfs *)  266,268,255
+long    unshare(unsigned long)  337,310,303
 
 # time
 int           pause ()                       29