common.mk: reinstall target

* common.mk (reinstall): new target.

* defs/gmake.mk (install, uninstall): can't run parallel.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39618 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
rbinstall.rb: gem subdirectories

* tool/rbinstall.rb (gem): Gem.ensure_gem_subdirectories now has mode
  option since r39607.  refix of r38870.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39619 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2013-03-07

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39620 b2dd03c8-39d4-4d8f-98ff-823fe69b080e