linux: Add P_PIDFD

It was added on Linux 5.4 (3695eae5fee0605f316fbaad0b9e3de791d7dfaf)
to extend waitid to wait on pidfd.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

posix/Makefile

@@ -32,7 +32,7 @@ headers	:= sys/utsname.h sys/times.h sys/wait.h sys/types.h unistd.h	      \
 	   bits/waitflags.h bits/waitstatus.h sys/unistd.h sched.h	      \
 	   bits/sched.h bits/cpu-set.h re_comp.h wait.h bits/environments.h   \
 	   cpio.h spawn.h bits/unistd.h bits/types/struct_sched_param.h	      \
-	   bits/unistd_ext.h
+	   bits/unistd_ext.h bits/types/idtype_t.h
 
 routines :=								      \
 	uname								      \

posix/sys/wait.h

@@ -71,12 +71,7 @@ typedef __pid_t pid_t;
 
 /* The following values are used by the `waitid' function.  */
 #if defined __USE_XOPEN_EXTENDED || defined __USE_XOPEN2K8
-typedef enum
+# include <bits/types/idtype_t.h>
-{
-  P_ALL,		/* Wait for any child.  */
-  P_PID,		/* Wait for specified process.  */
-  P_PGID		/* Wait for members of process group.  */
-} idtype_t;
 #endif
 
 

sysdeps/mach/hurd/bits/types/idtype_t.h

@@ -0,0 +1,12 @@
+#ifndef __idtype_t_defined
+#define __idtype_t_defined
+
+/* The following values are used by the `waitid' function.  */
+typedef enum
+{
+  P_ALL,		/* Wait for any child.  */
+  P_PID,		/* Wait for specified process.  */
+  P_PGID,		/* Wait for members of process group.  */
+} idtype_t;
+
+#endif

sysdeps/unix/sysv/linux/bits/types/idtype_t.h

@@ -0,0 +1,14 @@
+#ifndef __idtype_t_defined
+#define __idtype_t_defined
+
+/* The following values are used by the `waitid' function.  */
+typedef enum
+{
+  P_ALL,		/* Wait for any child.  */
+  P_PID,		/* Wait for specified process.  */
+  P_PGID,		/* Wait for members of process group.  */
+  P_PIDFD,		/* Wait for the child referred by the PID file
+			   descriptor.  */
+} idtype_t;
+
+#endif