Remove make_diff set of tools

These are mostly obsoleted by the switch to git, and it's easier to
remove them than to update the incorrect documentation.

Discussion: https://postgr.es/m/CABUevEwmASMn4WRJ6RagBx43sj10ctfMHcMA_-7KA3pDYmwpJw@mail.gmail.com

src/tools/make_diff/README

-src/tools/make_diff/README
-
-scripts
-=======
-
-Here are some of the scripts I use to make development easier.
-
-First, I use 'cporig' on every file I am about to change.  This makes a
-copy with the extension .orig.  If an .orig already exists, I am warned.
-
-I can get really fancy with this.  I can do 'cporig *' and make a .orig
-for every file in the current directory.  I can:
-
-	cporig `grep -l HeapTuple *`
-
-If I use mkid (from ftp.postgreSQL.org), I can do:
-
-	cporig `lid -kn 'fsyncOff'`
-
-and get a copy of every file containing that word.  I can then do:
-
-	vi `find . -name '*.orig'`
-
-or even better (using mkid):
-
-	eid fsyncOff
-
-to edit all those files.
-
-When I am ready to generate a patch, I run 'difforig' command from the top of
-the source tree:
-
-I pipe the output of this to a file to hold my patch, and the file names
-it processes appear on my screen.  It creates a nice patch for me of all
-the files I used with cporig.
-
-Finally, I remove my old copies with 'rmorig'.
-
-Bruce Momjian

src/tools/make_diff/cporig

-#!/bin/sh
-
-# src/tools/make_diff/cporig
-
-for FILE
-do
-	if [ ! -f "$FILE.orig" ]
-	then	cp $FILE $FILE.orig
-	else	echo "$FILE.orig exists" 1>&2
-	fi
-done

src/tools/make_diff/difforig

-#!/bin/sh
-
-# src/tools/make_diff/difforig
-
-if [ "$#" -eq 0 ]
-then	APATH="."
-else	APATH="$1"
-fi
-find $APATH -name '*.orig' -print | sort | while read FILE
-do
-	NEW="`dirname $FILE`/`basename $FILE .orig`"
-	echo "$NEW" 1>&2
-	diff -c $FILE $NEW
-done

src/tools/make_diff/rmorig

-#!/bin/sh
-
-# src/tools/make_diff/rmorig
-
-if [ "$#" -eq 0 ]
-then	APATH="."
-else	APATH="$1"
-fi
-find $APATH -name '*.orig' -exec rm {} \;