Fix Baseclass becomes! subclass.
Bring type casting behavior of hstore/json in line with serialized

`@raw_attributes` should not contain the type-cast, mutable version of
the value.
Removed CaptureHelper#flush_output_buffer as it is only used in tests.
reviewed: @tenderlove
Fix behavior of handling BC era dates.

BC era year is (astronomical year + 1) and starts from 1 BC.
document include_blank's usage with a string [ci skip]
Avoid hardcoded value in test setup/teardown.
Merge pull request #15525 from zuhao/refactor_actionpack_query_string_parsing_test

Avoid hardcoded value in test setup/teardown.
Mime::PNG is already defined.
Merge pull request #15521 from edogawaconan/fix_bc_postgres_master

Fix BC year handling in postgres
Merge pull request #15529 from zuhao/refactor_actionpack_mime_type_test

Make sure Mime::Type is not altered after tests.
Reset callbacks after test.

Otherwise the state of callback chain is leaked.
Avoid hard-coded value in test setup/teardown.
Restore Response.default_headers after test.
Merge pull request #15531 from zuhao/refactor_actionpack_request_test

Avoid hard-coded value in test setup/teardown.
Merge pull request #15532 from zuhao/refactor_actionpack_response_test

Restore Response.default_headers after test.
Merge pull request #15523 from gregmolnar/doc_fix

document include_blank's usage with a string [ci skip]
Merge pull request #15513 from zenspider/remove_flush_output_buffer

Removed CaptureHelper#flush_output_buffer as it is only used in tests.
Merge pull request #15530 from zuhao/refactor_actionpack_reloader_test

Reset callbacks after test.
Avoid misuse of underscore argument

Per convention, underscore-only argument names should be used for unused parameters.
Merge pull request #15535 from coreyward/patch-1

Avoid misuse of underscore argument