Revert "Merge pull request #9206 from ranjaykrishna/use_define_method"

This reverts commit 1fc6876b57f2e1d31731e74eb4271b5655e746d2, reversing
changes made to 0268b5d8cdc3c5a1337462135f0a326a2654ba1a.

Reason: failing test

  1) Error:
test_valid_column(ActiveRecord::ConnectionAdapters::SQLite3AdapterTest):
NoMethodError: undefined method `column' for
    test/cases/adapters/sqlite3/sqlite3_adapter_test.rb:29:in
`test_valid_column'
Revert "Revert "Merge pull request #9206 from ranjaykrishna/use_define_method""

This reverts commit 8aa4603a5adaa56c818a7bd1c0b761b4ecca3d3e.

Reverting the revert because I reverted the wrong thing! Fail.
Revert "checking in the abstractions for valid type checking:"

This reverts commit c321b309a9a90bbfa0912832c11b3fef52e71840.

Conflicts:
	activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
	activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

Reason: failing test

  1) Error:
test_valid_column(ActiveRecord::ConnectionAdapters::SQLite3AdapterTest):
NoMethodError: undefined method `column' for
    test/cases/adapters/sqlite3/sqlite3_adapter_test.rb:29:in
`test_valid_column'
Revert "Make valid_type? public"

This reverts commit 5d528f835e871f5f9d4b68e8a81cfbe900b7e718.

Relates to f8c8ad5 which is also getting reverted due to failing test.
copy edits [ci skip]
Merge branch 'master' of github.com:lifo/docrails

Conflicts:
	guides/source/upgrading_ruby_on_rails.md
Remove valid_type? method

It was supposed to be removed by the preceding two reversions but I did
them in the wrong order.
Removed an old require of an MD5 digest which is no longer used.
copy-edits RDoc in fba496f

This revision makes the terminology uniform with the rest of the file.
In general we describe these methods in terms of the adapter, rather
than the database. (As a side note, if we wanted to refer to the
database we would write "PostgreSQL".)
Merge pull request #9307 from wangjohn/remove_unneeded_md5_digest

Removed an old require of an MD5 digest which is no longer used.
Add CHANGELOG entry for 41ff6a10216f48f43605a1f9cd6094765cab750f

[ci skip]
add tests for ActiveRecord::Base#create
Merge pull request #9312 from Takehiro-Adachi/add_tests_for_ar_create

Add test for ActiveRecord::Base#create
Return false on toggle on error pages
Merge pull request #9313 from bkzl/return-false-on-toggle-on-error-pages

Return false in toggle function on error pages
clarify singular and plural routes

Found the wording on line 158 somewhat confusing. Added short example to clarify.
Gist URLs are now namespaced

see: https://github.com/blog/1406-namespaced-gists
Bump up minitest dependency and remove our own reinvented version of ParallelEach
Update guides/source/active_record_querying.md

Fix missing `ORDER BY id ASC` for Client.first(2);
Uppercase the little y in the SQL equivalent of the Client.last(2).
Document changes in #7968