Move away from the __ARCH_WANT_SYSCALL_NO_AT system calls.

Modern architectures only get the *at(2) system calls. For example,
aarch64 doesn't have open(2), and expects userspace to use openat(2)
instead.

Change-Id: I87b4ed79790cb8a80844f5544ac1a13fda26c7b5
diff --git a/libc/include/sys/stat.h b/libc/include/sys/stat.h
index 84e367f..ece44c6 100644
--- a/libc/include/sys/stat.h
+++ b/libc/include/sys/stat.h
@@ -180,11 +180,10 @@
 
 extern int mkfifo(const char*, mode_t);
 
-extern int  fstatat(int dirfd, const char *path, struct stat *buf, int flags);
-extern int  mkdirat(int dirfd, const char *pathname, mode_t mode);
-extern int fchownat(int dirfd, const char *path, uid_t owner, gid_t group, int flags);
-extern int fchmodat(int dirfd, const char *path, mode_t mode, int flags);
-extern int renameat(int olddirfd, const char *oldpath, int newdirfd, const char *newpath);
+extern int fchmodat(int, const char*, mode_t, int);
+extern int fstatat(int, const char*, struct stat*, int);
+extern int mkdirat(int, const char*, mode_t);
+extern int mknodat(int, const char*, mode_t, dev_t);
 
 # define UTIME_NOW      ((1l << 30) - 1l)
 # define UTIME_OMIT     ((1l << 30) - 2l)