parallel.rb: fix test-all parallel failure

* lib/test/unit/parallel.rb: fix test-all parallel failure if a test
  is skipped after raise.
  DL::TestFunc#test_sinf is skipped after raise on mingw ruby.
  But it causes Mashal.load failure due to undefined class/module
  DL::DLError when doing test-all parallel and test-all doesn't
  complete. We create new MiniTest::Skip object to avoid Mashal.load
  failure.
  [ruby-core:62133] [Bug #9767]

* test/testunit/test_parallel.rb (TestParallel): add a test.

* test/testunit/tests_for_parallel/ptest_forth.rb: ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45953 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
configure.in: enable SSE2 on mingw

* configure.in: enable SSE2 on mingw. target='i386-pc-mingw32'.
  [ruby-core:62095] [Bug #8358]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45954 b2dd03c8-39d4-4d8f-98ff-823fe69b080e