Making test accurately reflect what is going on in the schema migrations test
Merge pull request #8280 from asanghi/fix_guide_field_with_error_proc

fix guide with field_with_error proc example

[ci skip]
backport #8291, prevent mass assignment of polymorphic type with `build`

Closes #8265

Conflicts:

	activerecord/CHANGELOG.md
	activerecord/lib/active_record/associations/association.rb
Merge pull request #8295 from senny/8265_backport

backport #8291, prevent mass assignment of polymorphic type with `build`
Merge pull request #8311 from alisdair/dirty-nullable-datetime

Don't call will_change! for datetime nil->"".

Setting a nil datetime attribute to a blank string should not cause the
attribute to be dirty.

Conflicts:
	activerecord/CHANGELOG.md
	activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
speed up fixture loading by querying the schema cache for column names
schema cache already has the columns as a hash, so use that
Add i18n scope to disance_of_time_in_words.

This is a backport of rails/rails#7997.
Merge pull request #8321 from steveklabnik/backport_7997

Add i18n scope to disance_of_time_in_words.
@steveklabnik can't spell 'distance.'
Merge pull request #8325 from steveklabnik/backport_7997

@steveklabnik can't spell 'distance.' [ci skip]
schema cache already has the columns as a hash, so use that

Commits

  978ec98c8eff824a60c7e973f369cc7bed1f4d36 and
  51676652a3568ad09b06385564de4fdcb13af05e

changed database statements to use the schema_cache methods, added on
master in

  c99e34e90d763c52cbe8dc3d950ed1b4db665dc4 and
  dc973e78560a6514ab172f0ee86dc84a9147d39a

But apparently the methods weren't added to schema_cache, resulting in
the failure described in #8322 for 3-2-stable.

Fixes #8322.

Conflicts:
	activerecord/lib/active_record/connection_adapters/schema_cache.rb
Accept symbols as #send_data :disposition value
Use 1.8 hash style in pg specific schema
Work around undiagnosed bug that's draining a relation's bind_values
Merge pull request #8327 from elia/fix-send-data-disposition-with-symbols

Accept symbols as #send_data :disposition value
Merge pull request #7689 from cbarton/assume_migration_version_with_prefix_fix

Fixing a schema:load when using a prefix and suffix on the tables [Reopen/backport]
Merge pull request #8352 from steveklabnik/update_7858

Specify type of singular assication during serialization
Conflicts:
	activemodel/CHANGELOG.md
	activemodel/test/cases/serializers/xml_serialization_test.rb
Backport 78b30fed9336336694fb2cb5d2825f95800b541c to fix non-utf-8 databases mistakenly getting utf8 collation
Fixed description for ActiveSupport::Concern typical case