ARROW-7959: [Ruby] Add support for Ruby 2.3 again

Ruby 2.3 reached EOL but Ubuntu 16.04 LTS ships Ruby 2.3. So
supporting Ruby 2.3 again is valuable.

Note that Red Arrow 0.15.1 works with Ruby 2.3.

Closes #6501 from kou/ruby-add-support-for-ruby-2.3 and squashes the following commits:

f320181 <Sutou Kouhei>  Add support for Ruby 2.3 again

Authored-by: Sutou Kouhei <kou@clear-code.com>
Signed-off-by: Yosuke Shiro <yosuke.shiro615@gmail.com>

.github/workflows/cpp.yml

@@ -93,7 +93,7 @@ jobs:
         run: |
           docker login -u ${{ secrets.DOCKERHUB_USER }} \
                        -p ${{ secrets.DOCKERHUB_TOKEN }}
-          docker-compose push ubuntu-cpp
+          docker-compose push ubuntu-cpp-sanitizer
 
   macos:
     name: AMD64 MacOS 10.15 C++

.github/workflows/ruby.yml

@@ -41,7 +41,9 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ubuntu: [18.04]
+        ubuntu:
+          - 16.04
+          - 18.04
     env:
       UBUNTU: ${{ matrix.ubuntu }}
     steps:
@@ -71,6 +73,7 @@ jobs:
         run: |
           docker login -u ${{ secrets.DOCKERHUB_USER }} \
                        -p ${{ secrets.DOCKERHUB_TOKEN }}
+          docker-compose push ubuntu-c-glib
           docker-compose push ubuntu-ruby
 
   macos:

c_glib/test/test-numeric-array.rb

@@ -20,7 +20,7 @@ class TestNumericArray < Test::Unit::TestCase
 
   def test_mean
     array = build_double_array([1.1, 2.2, nil])
-    assert_in_delta(array.values.sum / 2,
+    assert_in_delta(array.values.inject(&:+) / 2,
                     array.mean)
   end
 end

ruby/red-arrow/lib/arrow/generic-filterable.rb

@@ -19,8 +19,8 @@ module Arrow
   module GenericFilterable
     class << self
       def included(base)
-        base.alias_method :filter_raw, :filter
-        base.alias_method :filter, :filter_generic
+        base.__send__(:alias_method, :filter_raw, :filter)
+        base.__send__(:alias_method, :filter, :filter_generic)
       end
     end
 

ruby/red-arrow/lib/arrow/generic-takeable.rb

@@ -19,8 +19,8 @@ module Arrow
   module GenericTakeable
     class << self
       def included(base)
-        base.alias_method :take_raw, :take
-        base.alias_method :take, :take_generic
+        base.__send__(:alias_method, :take_raw, :take)
+        base.__send__(:alias_method, :take, :take_generic)
       end
     end
 

ruby/red-arrow/lib/arrow/null-array-builder.rb

@@ -19,7 +19,7 @@ module Arrow
   class NullArrayBuilder
     class << self
       def buildable?(args)
-        super and args.collect(&:class) != [Integer]
+        super and not (args.size == 1 and args[0].is_a?(Integer))
       end
     end
   end