remove obsolete code as old actionmailer api was removed

Support decimal{1,2} and decimal{1-2} and decimal{1.2} so it works fine with bash, zsh, etc, closes #4602

Conflicts:

	railties/test/generators/migration_generator_test.rb

Fixed regression - unable to use a range as choices for form.select.

Fix typo

Fix setting $rails_rake_task variable.

some modifications in action_mailer/base.rb

Some end with a full stop, some don't. Let's have attention to detail
and make them uniform. I have chosen to add full stops according to
our documentation guidelines related to RDoc.

Fix `$rails_rake_task` global variable warning without replacing the value of $rails_rake_task if it is already set.

Fixes #4591.

Remove not used requires from csrf helper file and test

These requires were added in a87b92db and the implementation changed in
2cdc1f0c, removing the need for them.

Remove ActiveSupport::TestCase#pending, use `skip` instead

This reverts commit ecac7c96.

Reason: Changelogs are not meant to be changed from docrails.

change AR default_timezone to :utc since it's the default for AR::Railtie

Replace regexp matching with a simple string manipulation.

Using regexp looks like overkill here and is also 2x slower.

             user     system      total        real
string   0.020000   0.000000   0.020000 (  0.016256)
regexp   0.030000   0.000000   0.030000 (  0.035360)

require "benchmark"

names = ("a".."z").map { |c| c + "a" * rand(5..10) + "=" * rand(0..1) }.map(&:to_sym)
puts names

n = 1000
Benchmark.bmbm do |x|
  x.report "string" do
    n.times do
      names.each do |name|
        string_name = name.to_s
        string_name.chomp!('=')
        string_name
      end
    end
  end

  x.report "regexp" do
    n.times do
      names.each do |name|
        name.to_s =~ /(.*)=$/
        $1
      end
    end
  end
end

Refactor NumberHelpers