INIT: remove unused 'filter' utility

I could not even find any use of it in the ast-open-archive repo
which has the complete AST code.

src/cmd/INIT/Mamfile

@@ -231,42 +231,6 @@ make install
 		exec - esac
 		exec - test -w execrate -a -x execrate || chmod u+w,+x execrate
 	done execrate generated
-	make filter
-		make filter.sh
-		done filter.sh
-		prev filter.sh
-		exec - case static,port:$OPTIND:$RANDOM in
-		exec - ?*:*:*|*::*|*:*:$RANDOM)
-		exec - ;;
-		exec - *) if ENV= LC_ALL=C x= $SHELL -nc '[[ a || b ]] && : ${list[level]}  !(pattern)' 2>/dev/null
-		exec - then if grep '### .*archaic.* ###' >/dev/null
-		exec - then : filter contains archaic constructs :
-		exec - else ENV= LC_ALL=C $SHELL -n filter.sh
-		exec - fi
-		exec - fi
-		exec - ;;
-		exec - esac
-		exec - case '${mam_cc_SHELLMAGIC}' in
-		exec - "") case 184 in
-		exec - 0) cp filter.sh filter
-		exec - ;;
-		exec - *) {
-		exec - i=`(read x; echo $x) < filter.sh`
-		exec - case $i in
-		exec - '#!'*|*'||'*|':'*|'":"'*|"':'"*) echo "$i" ;;
-		exec - esac
-		exec - cat filter.sh
-		exec - } > filter
-		exec - ;;
-		exec - esac
-		exec - ;;
-		exec - *) cat - filter.sh > filter <<'!'
-		exec - ${mam_cc_SHELLMAGIC}
-		exec - !
-		exec - ;;
-		exec - esac
-		exec - test -w filter -a -x filter || chmod u+w,+x filter
-	done filter generated
 	make ignore
 		make ignore.sh
 		done ignore.sh
@@ -529,10 +493,6 @@ make install
 		prev crossexec
 		exec - ${STDCMP} 2>/dev/null -s crossexec ${INSTALLROOT}/bin/crossexec || { ${STDMV} ${INSTALLROOT}/bin/crossexec ${INSTALLROOT}/bin/crossexec.old 2>/dev/null || true; ${STDCP} crossexec ${INSTALLROOT}/bin/crossexec ;}
 	done ${INSTALLROOT}/bin/crossexec generated
-	make ${INSTALLROOT}/bin/filter
-		prev filter
-		exec - ${STDCMP} 2>/dev/null -s filter ${INSTALLROOT}/bin/filter || { ${STDMV} ${INSTALLROOT}/bin/filter ${INSTALLROOT}/bin/filter.old 2>/dev/null || true; ${STDCP} filter ${INSTALLROOT}/bin/filter ;}
-	done ${INSTALLROOT}/bin/filter generated
 	make ${INSTALLROOT}/bin/mamake
 		prev mamake
 		exec - ${STDCMP} 2>/dev/null -s mamake ${INSTALLROOT}/bin/mamake || { ${STDMV} ${INSTALLROOT}/bin/mamake ${INSTALLROOT}/bin/mamake.old 2>/dev/null || true; ${STDCP} mamake ${INSTALLROOT}/bin/mamake ;}