Revert "Merge pull request #1130 from rspec/deprecation_formatter_fix_299"

This reverts commit c63dc74b8b4b5f5f7ba89aa5405ee862130818f2, reversing
changes made to 64ba91330df9e8d8cd47f7831e25f19089af4361.

We're reverting this because this didn't actually solve the problem
of issueing deprecation warnings from option_parser.rb.
Default `output_stream` to $stdout.

This is what the docs say we do. It's also necessary
so that if `configuration.reporter` is accessed before
the CommandLine class has set the output_stream, it
uses $stdout as its output rather than a `StringIO.new`.

Before, issuing a deprecation from `option_parser.rb`
was causing no spec output at all since that happened
before the output_stream was set.
Fix a couple specs so that they explicitly redirect unwanted output.

These specs depended on the reporter defaulting
to a `StringIO.new`. Now that it is defaulting to
`$stdout`, we were getting unwanted output from these
two specs.
Use `output_stream` as the standardized method name.

Everything else in RSpec uses `output_stream`.
Warn if output_stream is changed after it has already been used by the reporter.
Deprecate `out` and `output` aliases of `output_stream`.

There's no reason for us to have the complexity of
3 names for the same thing.
Address ruby warning.
Add changelog entry.
Ruby 1.8 lacks public_send.
Merge pull request #1141 from rspec/fix-1127

Fix 1127 in 2-99-maintenance