Cache metadata in advance to avoid extra sql statements while testing.

Reason: If metadata is not cached extra sql statements
will be executed, which causes failures tests with assert_queries().
Make connection pool fair with respect to waiting threads.

The core of this fix is a threadsafe, fair Queue class.  It is
very similar to Queue in stdlib except that it supports waiting
with a timeout.

The issue this solves is that if several threads are contending for
database connections, an unfair queue makes is possible that a thread
will timeout even while other threads successfully acquire and release
connections.  A fair queue means the thread that has been waiting the
longest will get the next available connection.

This includes a few test fixes to avoid test ordering issues that
cropped up during development of this patch.
add convenience methods for checking migrations

if a rails project needs to be migrated ActiveRecord::Migrator.needs_migration? will be true or false if the current version matches the last version. 
The resolver tests fail if the mysql gem is not installed; this breaks
being able to run the sqlite3 tests without that gem. This fix ensures
the tests will only run if the mysql gem is installed.

A better solution might be to move these tests into the per-adapter tests,
and test each adapter's resolver.
Add failing test for 3.2.5  datetime attribute regression
Fix #6591. If a field with timezone isn't changed, we don't call will_change!.
Merge pull request #6619 from kennyj/fix_6591

Fix #6591 Rails 3.2.5 Regression: incorrect _changed? for datetimes
accept a block in button helper.
Fixed the Gemfile when gemspec is skipped in the 'rails plugin new' command
Metal controller doesn't have logger method, check it and then delegate
Merge pull request #6630 from route/logger_in_metal

Metal controller doesn't have logger method, check it and then delegate
Merge pull request #6628 from fredwu/fix_skip_gemspec

Fixed the Gemfile when gemspec is skipped in the 'rails plugin new' command
Merge pull request #6631 from yuki24/use_block_in_button_helper

Accept a block in FormHelper#button
One-liner code for logger in ActionView::Helpers::ControllerHelper
Merge pull request #6632 from route/one_line_code_for_logger

One-liner code for logger in ActionView::Helpers::ControllerHelper
Merge pull request #6616 from dpassage/fix_resolver_test_sqlite3

Resolver tests fail if mysql adapter not installed
add instance_accessor option to ActiveSupport::Configurable#config_accessor

Changes:

* Add `instance_accessor` option to opt out of the instance writer and
  instance reader methods.
* Raises a NameError if the name of the attribute is not valid.
* Update documentation and tests.
* Add CHANGELOG entry in activesupport.
bundle exec rake assets:precompile shouldn't fail quietly.

If JavaScript runtime is not installed, execjs fails with error quietly,
while tests continue to run. This should not happen since it causes tests
to fail for unknown reason (#6621).

This commit assures that if JavaScript runtime is not installed, an assertion
is raised.
Merge pull request #6638 from frodsan/config_accessor

add instance_accessor option to config_accessor
Merge pull request #6627 from Vanuan/tests_add_precompile_failure_assert

bundle exec rake assets:precompile shouldn't fail quietly.