rubygems/rubygems — pull request #377 by kou (2012-09-23 12:13:31+00:00)
Title: Support normal gem require without explicit 'gem "name"' for default gem

Let "test-unit" is a default gem.

Before:

```ruby
require "test/unit" # -> test/unit.rb of the standard library is loaded

gem "test-unit"
require "test/unit" # -> test/unit.rb test-unit gem is loaded
```

After:

```ruby
require "test/unit" # -> test/unit.rb of test-unit gem is loaded
```

Default gem related works are not completed. There are following
not implemented features:

* Register the default gems
* Support "gem contents" for RDoc
* Block "gem uninstall default-gem"

This change shows what I want to do for implementing default gem. If
you accept this change, I will do the next works.

Note that I want to move Kerenel#require codes in
lib/rubygems/custom_require.rb to Gem::CustomRequire#run in the
future.