cmd/5l,cmd/6l,cmd/8l: fix dragonflydynld path

R=golang-dev, bradfitz, dave
CC=golang-dev
https://codereview.appspot.com/13225043
runtime: record type information for hashtable internal structures.
Remove all hashtable-specific GC code.

Fixes bug 6119.

R=cshapiro, dvyukov, khr
CC=golang-dev
https://codereview.appspot.com/13078044