Add compatibility for to_h with block in Ruby 2.5

Author: marcandre

lib/ostruct.rb

@@ -122,11 +122,21 @@ def initialize_copy(orig) # :nodoc:
   #   data.to_h {|name, value| [name.to_s, value.upcase] }
   #               # => {"country" => "AUSTRALIA", "capital" => "CANBERRA" }
   #
-  def to_h(&block)
-    if block_given?
-      @table.to_h(&block)
-    else
-      @table.dup
+  if {test: :to_h}.to_h{ [:works, true] }[:works] # RUBY_VERSION < 2.6 compatibility
+    def to_h(&block)
+      if block_given?
+        @table.to_h(&block)
+      else
+        @table.dup
+      end
+    end
+  else
+    def to_h(&block)
+      if block_given?
+        @table.map(&block).to_h
+      else
+        @table.dup
+      end
     end
   end