[2.26 COMMITTED] linux ttyname: Update a reference to kernel docs for kernel 4.10

[Florian Weimer]

From: Luke Shumaker <lukeshu@parabola.nu>

Linux 4.10 moved many of the documentation files around.

4.10 came out between the time the patch adding the comment (commit
15e9a4f378c8607c2ae1aa465436af4321db0e23) was submitted and the time
it was applied (in February, January, and March 2017; respectively).

Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com>
(cherry picked from commit 9b5a87502d048905c383b65c51768f4a1db8c685)

2017-11-15  Luke Shumaker  <lukeshu@parabola.nu>

	* sysdeps/unix/sysv/linux/ttyname.h (is_pty): Update doc reference.

diff --git a/sysdeps/unix/sysv/linux/ttyname.h b/sysdeps/unix/sysv/linux/ttyname.h
index 2e415e4e9c..cbcdbab607 100644
--- a/sysdeps/unix/sysv/linux/ttyname.h
+++ b/sysdeps/unix/sysv/linux/ttyname.h
@@ -21,7 +21,8 @@
 #include <sys/stat.h>
 
 /* Return true if this is a UNIX98 pty device, as defined in
-   linux/Documentation/devices.txt.  */
+   linux/Documentation/devices.txt (on linux < 4.10) or
+   linux/Documentation/admin-guide/devices.txt (on linux >= 4.10).  */
 static inline int
 is_pty (struct stat64 *sb)
 {