unix: don't use deprecated syscalls on linux/arm64

On linux/arm64 we used to manually define syscall numbers for some
deprecated syscalls. Most of them are unused by now anyhow. Convert the
remaining syscall wrappers using them to implement the respective
functionality using a non-deprecated syscall (in the same way glibc does
it):

- Implement EpollCreate using EpollCreate1 and additionally check
  that the passed size argument is larger than 0.
- Implement Futimesat and utimes using utimensat. Also change futimesat
  on the other geese to take a string instead of *byte and let the
  generated wrapper do the BytePtrFromString conversion.
- Return ENOSYS from Ustat. The ustat syscall has been deprecated for a
  long time in favor of fstatfs and statfs. Even glibc will deprecate
  ustat in the upcoming 2.28 release [1].

[1] https://sourceware.org/git/?p=glibc.git;a=blob;f=NEWS;h=d51fa09544f03899b7ff5a80569db088c3c23c28;hb=HEAD#l90

Change-Id: I7ea38a3cd394b0875f17443b14e107fd9c70350d
Reviewed-on: https://go-review.googlesource.com/119655
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/unix/syscall_linux_arm.go b/unix/syscall_linux_arm.go
index c59f858..3ec7a93 100644
--- a/unix/syscall_linux_arm.go
+++ b/unix/syscall_linux_arm.go
@@ -75,6 +75,8 @@
 // 64-bit file system and 32-bit uid calls
 // (16-bit uid calls are not always supported in newer kernels)
 //sys	Dup2(oldfd int, newfd int) (err error)
+//sysnb	EpollCreate(size int) (fd int, err error)
+//sys	EpollWait(epfd int, events []EpollEvent, msec int) (n int, err error)
 //sys	Fchown(fd int, uid int, gid int) (err error) = SYS_FCHOWN32
 //sys	Fstat(fd int, stat *Stat_t) (err error) = SYS_FSTAT64
 //sys	Fstatat(dirfd int, path string, stat *Stat_t, flags int) (err error) = SYS_FSTATAT64
@@ -86,6 +88,7 @@
 //sys	Lchown(path string, uid int, gid int) (err error) = SYS_LCHOWN32
 //sys	Listen(s int, n int) (err error)
 //sys	Lstat(path string, stat *Stat_t) (err error) = SYS_LSTAT64
+//sys	Pause() (err error)
 //sys	sendfile(outfd int, infd int, offset *int64, count int) (written int, err error) = SYS_SENDFILE64
 //sys	Select(nfd int, r *FdSet, w *FdSet, e *FdSet, timeout *Timeval) (n int, err error) = SYS__NEWSELECT
 //sys	Setfsgid(gid int) (err error) = SYS_SETFSGID32
@@ -97,11 +100,10 @@
 //sys	Shutdown(fd int, how int) (err error)
 //sys	Splice(rfd int, roff *int64, wfd int, woff *int64, len int, flags int) (n int, err error)
 //sys	Stat(path string, stat *Stat_t) (err error) = SYS_STAT64
+//sys	Ustat(dev int, ubuf *Ustat_t) (err error)
 
-// Vsyscalls on amd64.
+//sys	futimesat(dirfd int, path string, times *[2]Timeval) (err error)
 //sysnb	Gettimeofday(tv *Timeval) (err error)
-//sys	EpollWait(epfd int, events []EpollEvent, msec int) (n int, err error)
-//sys	Pause() (err error)
 
 func Time(t *Time_t) (Time_t, error) {
 	var tv Timeval
@@ -123,6 +125,8 @@
 	return Utimes(path, tv)
 }
 
+//sys	utimes(path string, times *[2]Timeval) (err error)
+
 //sys   Pread(fd int, p []byte, offset int64) (n int, err error) = SYS_PREAD64
 //sys   Pwrite(fd int, p []byte, offset int64) (n int, err error) = SYS_PWRITE64
 //sys	Truncate(path string, length int64) (err error) = SYS_TRUNCATE64