Retire ptrace(T_DUMPCORE), dumpcore(1), gcore(1)

The T_DUMPCORE implementation was not only broken - it would currently
produce a coredump of the tracer process rather than the traced
process - but also deeply flawed, and fixing it would require serious
alteration of PM's internal state machine. It should be possible to
implement the same functionality in userland, and that is now the
suggested way forward. For now, also remove the (identical) utilities
using T_DUMPCORE: dumpcore(1) and gcore(1).

Change-Id: I1d51be19c739362b8a5833de949b76382a1edbcc

man/man1/Makefile

@@ -3,7 +3,7 @@ MAN=	ash.1 at.1 \
 	chmod.1 cmp.1 compress.1 \
 	cp.1 crc.1 crontab.1 dd.1 \
 	dhrystone.1 dosdir.1 dosread.1 doswrite.1 \
-	dumpcore.1 eject.1 \
+	eject.1 \
 	factor.1 \
 	flexdoc.1 format.1 fortune.1 \
 	fsck.mfs.1 host.1 hostaddr.1 ifdef.1 \

man/man1/dumpcore.1

@@ -1,29 +0,0 @@
-.TH DUMPCORE 1
-.SH NAME
-dumpcore \- generate core file of running process
-.SH SYNOPSIS
-dumpcore \fIpid\fR
-.br
-.de FL
-.TP
-\\fB\\$1\\fR
-\\$2
-..
-.de EX
-.TP 20
-\\fB\\$1\\fR
-# \\$2
-..
-.SH DESCRIPTION
-The \fBdumpcore\fR utility generates a core file for a running process, based
-on that process's process ID (\fIpid\fP). The resulting core file will be
-stored under the name "core" in the current working directory. Any previous
-file with that name will be overwritten.
-.PP
-The resulting core file can be used with for example
-.BR mdb (1).
-.SH BUGS
-The process of generating the core file is currently very rudimentary, and
-the generated core file does not contain for example memory mapped areas.
-.SH "SEE ALSO"
-.BR mdb (1).