Added missing require for `gem uninstall --format-executable`.
The correct name of the executable being uninstalled is now displayed
with --format-executable.
Fixed `gem unpack uninstalled_gem` default version picker.
RubyGems no longer claims a nonexistent gem can be uninstalled.
`gem which` no longer claims directories are requirable files.
`gem cleanup` continues cleaning up gems if one can't be uninstalled
due to permissions. Issue #82.
Gem repository directories are no longer created world-writable.
Patch by Sakuro OZAWA. [Ruby 1.9 - Bug #4930]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@32852 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
