Added Winsock 2 to list of libraries to use when building for Windows

targets

mrbgem.rake

@@ -3,6 +3,12 @@ MRuby::Gem::Specification.new('mruby-socket') do |spec|
   spec.authors = 'Internet Initiative Japan'
 
   spec.cc.include_paths << "#{build.root}/src"
+  
+  # If Windows, use winsock
+  if ( /mswin|mingw|win32/ =~ RUBY_PLATFORM ) then
+    spec.linker.libraries << "wsock32"
+    spec.linker.libraries << "ws2_32"
+  end
 
   spec.add_dependency('mruby-io')
   spec.add_dependency('mruby-pack')