fix typos [ci skip]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56041 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -8,7 +8,7 @@ Tue Aug 30 14:53:34 2016  NAKAMURA Usaku  <usa@ruby-lang.org>
 	* io.c (nogvl_fsync, nogvl_fdatasync): on Windows, just ignore if the
 	  fd is associated to non-disk device.  if call fsync and/or fdatasync
 	  with such fds, it causes Errno::EBADF exception and the behavior is
-	  incomatible with ruby 2.1 and earlier unintendedly introduced.
+	  incompatible with ruby 2.1 and earlier unintentionally introduced.
 
 Tue Aug 30 03:38:35 2016  NARUSE, Yui  <naruse@ruby-lang.org>