test_io.rb: get rid of error message

* test/ruby/test_io.rb (TestIO#test_pid_after_close_read): get rid of
  broken pipe error message from invoked command, by let it exit
  silently.  echo in cmd.exe does not interpret double quotes.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43164 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
win32/file.c: check ASCII encodings first

* win32/file.c (code_page): check US-ASCII and ASCII-8bit before
  ordinary mapping.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43165 b2dd03c8-39d4-4d8f-98ff-823fe69b080e