pdwait4(2): Remove documentation of vaporware

This syscall has never existed and is not at risk of existing any time soon.
Remove documentation referencing it, which has been wrong since FreeBSD 9.

Reported by:	allanjude@

lib/libc/sys/Makefile.inc

@@ -421,8 +421,7 @@ MLINKS+=open.2 openat.2
 MLINKS+=pathconf.2 fpathconf.2
 MLINKS+=pathconf.2 lpathconf.2
 MLINKS+=pdfork.2 pdgetpid.2\
-	pdfork.2 pdkill.2 \
-	pdfork.2 pdwait4.2
+	pdfork.2 pdkill.2
 MLINKS+=pipe.2 pipe2.2
 MLINKS+=poll.2 ppoll.2
 MLINKS+=rctl_add_rule.2 rctl_get_limits.2 \

lib/libc/sys/pdfork.2

@@ -32,14 +32,13 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd June 8, 2016
+.Dd June 17, 2017
 .Dt PDFORK 2
 .Os
 .Sh NAME
 .Nm pdfork ,
 .Nm pdgetpid ,
-.Nm pdkill ,
-.Nm pdwait4
+.Nm pdkill
 .Nd System calls to manage process descriptors
 .Sh LIBRARY
 .Lb libc
@@ -51,8 +50,6 @@
 .Fn pdgetpid "int fd" "pid_t *pidp"
 .Ft int
 .Fn pdkill "int fd" "int signum"
-.Ft int
-.Fn pdwait4 "int fd" "int *status" "int options" "struct rusage *rusage"
 .Sh DESCRIPTION
 Process descriptors are special file descriptors that represent processes,
 and are created using
@@ -96,11 +93,6 @@ except that it accepts a process descriptor,
 .Fa fd ,
 rather than a PID.
 .Pp
-.Fn pdwait4
-behaves identically to
-.Xr wait4 2 ,
-but operates with respect to a process descriptor argument rather than a PID.
-.Pp
 The following system calls also have effects specific to process descriptors:
 .Pp
 .Xr fstat 2
@@ -146,9 +138,6 @@ does.
 and
 .Fn pdkill
 return 0 on success and -1 on failure.
-.Pp
-.Fn pdwait4
-returns a PID on success and -1 on failure.
 .Sh ERRORS
 These functions may return the same error numbers as their PID-based equivalents
 (e.g.
@@ -180,9 +169,8 @@ for
 The
 .Fn pdfork ,
 .Fn pdgetpid ,
-.Fn pdkill
 and
-.Fn pdwait4
+.Fn pdkill
 system calls first appeared in
 .Fx 9.0 .
 .Pp
@@ -197,6 +185,3 @@ and
 .An Jonathan Anderson Aq Mt jonathan@FreeBSD.org
 at the University of Cambridge Computer Laboratory with support from a grant
 from Google, Inc.
-.Sh BUGS
-.Fn pdwait4
-has not yet been implemented.

lib/libc/sys/wait.2

@@ -28,7 +28,7 @@
 .\"     @(#)wait.2	8.2 (Berkeley) 4/19/94
 .\" $FreeBSD$
 .\"
-.Dd June 1, 2016
+.Dd June 17, 2017
 .Dt WAIT 2
 .Os
 .Sh NAME
@@ -601,9 +601,7 @@ must be checked against zero to determine if a process reported status.
 called with -1 to wait for any child process will ignore a child that is
 referenced by a process descriptor (see
 .Xr pdfork 2 ) .
-Specific processes can still be waited on by specifying the process ID
-or descriptor (see
-.Xr pdwait 4 ) .
+Specific processes can still be waited on by specifying the process ID.
 .Sh ERRORS
 The
 .Fn wait