Import bigdecimal 1.4.2

* https://github.com/ruby/bigdecimal/compare/v1.4.1..v1.4.2

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66574 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/bigdecimal/bigdecimal.gemspec

@@ -1,6 +1,6 @@
 # coding: utf-8
 
-bigdecimal_version = '1.4.1'
+bigdecimal_version = '1.4.2'
 
 Gem::Specification.new do |s|
   s.name          = "bigdecimal"

ext/bigdecimal/util/extconf.rb

@@ -4,11 +4,11 @@ require 'mkmf'
 checking_for(checking_message("Windows")) do
   case RUBY_PLATFORM
   when /cygwin|mingw/
-    if defined?($extlist)
-      build_dir = "$(TARGET_SO_DIR)../"
-    else
+    if ARGV.include?('-rdevkit') # check `rake -rdevkit compile` case
       base_dir = File.expand_path('../../../..', __FILE__)
       build_dir = File.join(base_dir, "tmp", RUBY_PLATFORM, "bigdecimal", RUBY_VERSION, "")
+    else
+      build_dir = "$(TARGET_SO_DIR)../"
     end
     $libs << " #{build_dir}bigdecimal.so"
     true