[2.26 COMMITTED] linux ttyname: Change return type of is_pty from int to bool

[Florian Weimer]

From: Luke Shumaker <lukeshu@parabola.nu>

is_pty returning a bool is fine since there's no possible outcome other than
true or false, and bool is used throughout the codebase.

Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com>
(cherry picked from commit d10d6cab168ffa26ef6a506655ee5dc8537c8ed7)

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

	* sysdeps/unix/sysv/linux/ttyname.h (is_pty): Change return type from
	int to bool.

diff --git a/sysdeps/unix/sysv/linux/ttyname.h b/sysdeps/unix/sysv/linux/ttyname.h
index cbcdbab607..cdaf60fb87 100644
--- a/sysdeps/unix/sysv/linux/ttyname.h
+++ b/sysdeps/unix/sysv/linux/ttyname.h
@@ -16,6 +16,7 @@
    not, see <http://www.gnu.org/licenses/>.  */
 
 #include <unistd.h>
+#include <stdbool.h>
 #include <sys/sysmacros.h>
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -23,7 +24,7 @@
 /* Return true if this is a UNIX98 pty device, as defined in
    linux/Documentation/devices.txt (on linux < 4.10) or
    linux/Documentation/admin-guide/devices.txt (on linux >= 4.10).  */
-static inline int
+static inline bool
 is_pty (struct stat64 *sb)
 {
 #ifdef _STATBUF_ST_RDEV