remove references to hardcoded /usr/local/plan9 where possible

bin/lookman

@@ -1,7 +1,7 @@
-#!/usr/local/plan9/bin/rc
+#!/usr/bin/env $PLAN9/bin/rc
 # Usage: lookman key ...
 #	prints out the names of all manual pages containing all the given keywords
-index=/usr/local/plan9/man/lookman.index
+index=$PLAN9/man/lookman.index
 t1=/tmp/look1.$pid
 t2=/tmp/look2.$pid
 fn sigexit sigint sighup sigterm{
@@ -24,7 +24,7 @@ for(i in $*){
 			' > $t2
 	mv $t2 $t1
 }
-sort $t1 | sed 's;/usr/local/plan9/man/man[0-9]*/;;
+sort $t1 | sed 's;/.*/man/man[0-9]*/;;
 	s;(.*)\.(.*);man \2 \1 # \1(\2);'
 rm -f $t1 $t2
 exit 0