Creating a module so that per thread registries can be easily created as
thread local variables.
Created a runtime registry for thread local variables in active record.
Changed the ScopeRegistry and the InstrumentationRegistry to use the
PerThreadRegistry module.
Fix inflector to respect default locale.

The inflector was made aware of locales in 7db0b073fec6bc3e6f213b58c76e7f43fcc2ab97,
but it defaulted to :en. That should actually be our default
locale instead.

Fixes #10125
Merge pull request #10156 from wangjohn/grouping_thread_locals

Grouping thread locals in ActiveRecord
Merge pull request #10158 from steveklabnik/issue_10125

Fix inflector to respect default locale.
Add failing test case for #9654
Reverts rendering behavior when format is unknown

If a request has unknown format (eg. /foo.bar), the renderer
fallbacks to default format.

This patch reverts Rails 3.2 behavior after c2267db commit.

Fixes issue #9654.
Return nil for Mime::NullType#ref
Fixed typo
Merge pull request #10160 from choudhuryanupam/fix_typo_n_grammar

Fixed typo
Removed unused setup
Merge pull request #10162 from choudhuryanupam/fix_activesupport_test

Removed unused setup