* backport r39307 from trunk.  [Bug #7880]

* lib/rubygems/installer.rb:  Fixed placement of executables with
  --user-install.  [ruby-trunk - Bug #7779]

* test/rubygems/test_gem_installer.rb:  Test for above.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@39319 b2dd03c8-39d4-4d8f-98ff-823fe69b080e