io.c (rb_io_syswrite): add RB_GC_GUARD

* io.c (rb_io_syswrite): add RB_GC_GUARD
  [Bug #9472][ruby-core:60407]

git-svn-id: svn+ssh://svn.ruby-lang.org/ruby/trunk@44790 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-02-02

git-svn-id: svn+ssh://svn.ruby-lang.org/ruby/trunk@44791 b2dd03c8-39d4-4d8f-98ff-823fe69b080e