Add extended attribute (xattr) system call wrappers to bionic.

The xattr system calls are required for the SE Android userspace in
order to get and set file security contexts.  In particular, libselinux
requires these calls.

Change-Id: I78f5eb3d8f3384aed0a5e7c6a6f001781d982017
diff --git a/libc/SYSCALLS.TXT b/libc/SYSCALLS.TXT
index 5c1e36e..fc5f808 100644
--- a/libc/SYSCALLS.TXT
+++ b/libc/SYSCALLS.TXT
@@ -133,6 +133,10 @@
 int         fchownat(int dirfd, const char *path, uid_t owner, gid_t group, int flags)  325,298
 int         fchmodat(int dirfd, const char *path, mode_t mode, int flags)  333,306
 int         renameat(int olddirfd, const char *oldpath, int newdirfd, const char *newpath)  329,302
+int         fsetxattr(int, const char *, const void *, size_t, int) 228
+ssize_t     fgetxattr(int, const char *, void *, size_t) 231
+ssize_t     flistxattr(int, char *, size_t) 234
+int         fremovexattr(int, const char *) 237
 
 # file system
 int     link (const char*, const char*)  9
@@ -158,7 +162,16 @@
 int     symlink(const char *, const char *)  83
 int     fchdir(int)    133
 int     truncate(const char*, off_t)    92
+int     setxattr(const char *, const char *, const void *, size_t, int) 226
+int     lsetxattr(const char *, const char *, const void *, size_t, int) 227
+ssize_t getxattr(const char *, const char *, void *, size_t) 229
+ssize_t lgetxattr(const char *, const char *, void *, size_t) 230
+ssize_t listxattr(const char *, char *, size_t) 232
+ssize_t llistxattr(const char *, char *, size_t) 233
+int     removexattr(const char *, const char *) 235
+int     lremovexattr(const char *, const char *) 236
 int     __statfs64:statfs64(const char *, size_t, struct statfs *)  266,268
+
 # time
 int           pause ()                       29
 int           gettimeofday(struct timeval*, struct timezone*)       78