* common.mk: add new rules `gcbench-rdoc', `gcbench-hash'.
* tool/gcbench.rb: separate GC bench framework and process.
* tool/hashbench1.rb, tool/hashbench2.rb: add two types GC bench.
  hashbench1: many temporal objects (GC by newobj)
  hashbench2: hash size becomes bigger and bigger (GC by malloc)
  Two benchs are executed by `gcbench-hash' rule.
* tool/rdocbench.rb: separated.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41458 b2dd03c8-39d4-4d8f-98ff-823fe69b080e