This is neither a public API, nor used internally, so let's remove it.

Conflicts:
	activesupport/lib/active_support/multibyte/chars.rb

The docs for the String class indicate that methods like `rstrip!` and
others should return nil when they do not have an effect on the string.

People use this!
This reverts commit 071c8bf6.

The default pass-through to `method_missing` makes `#slice!` return
`self` rather than the string that was sliced off.

This test was actually specifying the opposite of what it should.

Runners are used internally.

This reverts commit 40c8aa70.

simplify Class#descendants using singleton_class method

correctly handle order calls after a reorder

Infer currency negative format from positive one.